[Federal Register Volume 66, Number 144 (Thursday, July 26, 2001)]
[Proposed Rules]
[Pages 38982-39004]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-18637]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. NHTSA 2000-8572]
RIN 2127-AI33
Federal Motor Vehicle Safety Standards: Tire Pressure Monitoring
Systems; Controls and Displays
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Notice of proposed rulemaking.
-----------------------------------------------------------------------
SUMMARY: The Transportation Recall Enhancement, Accountability, and
Documentation Act of 2000 mandates a rulemaking proceeding to require
motor vehicles to be equipped with a tire pressure monitoring system
that warns the driver a tire is significantly under-inflated. In
response, this document proposes to establish a new Federal Motor
Vehicle Safety Standard No. 138 that would require tire pressure
monitoring systems to be installed in new passenger cars and in new
light trucks and multipurpose passenger vehicles.
This document seeks comment on two alternative versions of the new
standard. One alternative would require that the driver be warned when
the tire pressure in one or more tires, up to a total of 4 tires, has
fallen to 20 percent or more below the vehicle manufacturer's
recommended cold inflation pressure for the vehicle's tires, or a
minimum level of pressure to be specified in the new standard,
whichever is higher. The other alternative would require that the
driver be warned when tire pressure in one or more tires, up to a total
of 3 tires, has fallen to 25 percent or more below the vehicle
manufacturer's recommended cold inflation pressure for the vehicle's
tires, or a minimum level of pressure to be specified in the new
standard, whichever is higher.
DATES: Comments must be received on or before September 6, 2001.
ADDRESSES: You may submit your comments in writing to: Docket Section,
National Highway Traffic Safety Administration, 400 Seventh Street,
SW., Washington, DC 20590. Alternatively, you may submit your comments
electronically by logging onto the Docket Management System (DMS)
website at http://dms.dot.gov. Click on ``Help & Information'' or
``Help/Info'' to view instructions for filing your comments
electronically. Regardless of how you submit your comments, you should
mention the docket number of this document. You can find the number at
the beginning of this document.
FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may call Mr.
George Soodoo or Mr. Joseph Scott, Office of Crash Avoidance Standards
(Telephone: 202-366-2720) (Fax: 202-366-4329).
For legal issues, you may call Mr. Dion Casey, Office of Chief
Counsel (Telephone: 202-366-2992) (Fax: 202-366-3820).
You may send mail to these officials at National Highway Traffic
Safety Administration, 400 Seventh Street, SW., Washington, DC 20590.
You may call Docket Management at 202-366-9324. You may visit the
Docket from 10 a.m. to 5 p.m., Monday through Friday.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Executive Summary
II. Background
A. The Transportation Recall Enhancement, Accountability, and
Documentation Act
B. Previous Rulemaking on Tire Pressure Monitoring Systems
III. Problem Description
A. Infrequent Consumer Monitoring of Tire Pressure
B. Loss of Tire Pressure Due to Natural and Other Causes
C. Percentage of Motor Vehicles With Under-Inflated Tires
D. Consequences of Under-Inflation of Tires
1. Reduced Vehicle Safety
2. Reduced Tread Life
3. Reduced Fuel Economy
IV. Tire Pressure Monitoring Systems
A. Indirect TPMSs
B. Direct TPMSs
C. Advantages and Disadvantages
1. Indirect TPMSs
2. Direct TPMSs
3. Tabular Summary of Advantages and Disadvantages of Indirect
and Direct TPMSs
V. Agency Proposal
A. Summary of Proposal
B. Vehicles Covered by This Proposal
C. Definition of ``Significantly Under-Inflated''
D. Low Tire Pressure Warning Telltale
1. Color
2. Symbol
3. Time Frame for Telltale Illumination
4. Duration of Warning
5. Self-Check
E. System Calibration and Reset
F. System Failure
G. Number of Tires Monitored
H. Replacement Tires/Rims
I. Monitoring of Spare Tire
J. Written Instructions
K. Temperature Compensation
L. Test Conditions
M. Test Procedures
N. Human Factors
VI. Benefits
A. First Alternative
[[Page 38983]]
B. Second Alternative
C. Unquantified Benefits
VII. Costs
A. Indirect TPMSs
B. Direct TPMSs
C. Testing and Maintenance Costs
D. Unquantified Costs
E. First Alternative
F. Second Alternative
VIII. Lead-Time
IX. Rulemaking Analyses and Notices
I. Executive Summary
This document proposes to establish a new Federal Motor Vehicle
Safety Standard that would require tire pressure monitoring systems
(TPMSs) to be installed in new passenger cars and in new light trucks
and multipurpose passenger vehicles. Each vehicle's system would
include a warning telltale that illuminates to inform the driver when
the vehicle has a significantly under-inflated tire.
This document seeks comment on two alternative versions of the new
standard. One alternative would require that the driver be warned when
the tire pressure in one or more tires, up to a total of 4 tires, has
fallen to 20 percent or more below the vehicle manufacturer's
recommended cold inflation pressure for the vehicle's tires, or a
minimum level of pressure to be specified in the new standard,
whichever pressure is higher. The other alternative would require that
the driver be warned when tire pressure in one or more tires, up to a
total of 3 tires, has fallen to 25 percent or more below the vehicle
manufacturer's recommended cold inflation pressure for the vehicle's
tires, or a minimum level of pressure to be specified in the new
standard, whichever pressure is higher.
To meet the first alternative, vehicle manufacturers would likely
need to install direct TPMSs. Direct TPMSs have a tire pressure sensor
in each tire.
To meet the second alternative, vehicle manufacturers could install
either direct or indirect TPMSs. Indirect TPMSs do not have tire
pressure sensors. Current indirect TPMSs rely on the presence of an
anti-lock braking system (ABS) to detect and compare differences in the
rotational speed of a vehicle's wheels. Wheel speed correlates to tire
pressure since the diameter of a tire decreases slightly as tire
pressure decreases. The second alternative would require only warnings
about pressure loss in up to three tires since most indirect TPMSs
cannot detect when all four tires lose pressure at roughly the same
rate and become significantly under-inflated.
NHTSA anticipates that vehicle manufacturers would minimize their
costs of complying with the second alternative by installing indirect
TPMSs in vehicles currently equipped with ABSs and direct TPMSs in
vehicles currently not so equipped. For vehicles already equipped with
an ABS, the cost of modifying that system to serve the additional
purpose of indirectly monitoring tire pressure would be significantly
less than the cost of adding a direct TPMS to those vehicles. For
vehicles not so equipped, adding a direct TPMS would be the less
expensive way of monitoring tire pressure.
NHTSA has two sets of data, one from Goodyear and another from the
agency's Vehicle Research and Testing Center (VRTC), on the effect of
under-inflated tires on a vehicle's stopping distance. The Goodyear
data indicate that a vehicle's stopping distance on wet surfaces is
significantly reduced when its tires are properly inflated, as compared
to when its tires are significantly under-inflated. The VRTC data
indicate little or no effect on a vehicle's stopping distance. For
purposes of this rulemaking, NHTSA is using the Goodyear data to
establish an upper bound of benefits and the VRTC data to establish a
lower bound. The estimates below are the mid-points between those upper
and lower bounds.
NHTSA estimates that the first alternative would prevent 10,635
injuries and 79 deaths at an average cost of $66.33 per vehicle.\1\
Since approximately 16 million vehicles are produced for sale in the
United States each year, the total annual cost of the first alternative
would be about $1.06 billion. However, if the average per vehicle fuel
and tread life savings ($32.22 and $11.03, respectively) over the
lifetime of the vehicle are factored in, the average net cost of the
first alternative drops to $23.08 per vehicle, and the total annual
cost drops to about $369 million ($1.06 billion-($516 million + $176
million)) . The second alternative would prevent 6,585 injuries and 49
deaths at an average cost of $30.54 per vehicle.\2\ Since approximately
16 million vehicles are produced for sale in the United States each
year, the total annual cost of the second alternative would be about
$489 million. However, if the average per vehicle fuel and tread wear
savings ($16.40 and $5.51, respectively) over the lifetime of the
vehicle are factored in, the average net cost of the second alternative
drops to $8.63 per vehicle, and the total annual cost drops to about
$138 million ($489 million-($263 million + 88 million). The net cost
per equivalent life saved would be $1.9 million for the first
alternative and $1.1 million for the second.
---------------------------------------------------------------------------
\1\ The range of injuries prevented would be 0 to 21,270, an the
range of deaths prevented would be 0 to 158.
\2\ The range of injuries prevented would be 0 to 13,170, an the
range of deaths prevented would be 0 to 97.
---------------------------------------------------------------------------
The agency believes the proposals would also result in other
benefits, such as fewer crashes resulting from tire blowouts, adverse
effects on vehicle handling due to inflation pressure loss and
hydroplaning, from fewer crashes involving vehicles that had been
stopped by the side of the road because of a flat tire, and the
prevention of the property damage that results from these crashes.
NHTSA has not attempted to quantify those benefits. Those unquantified
benefits would be greater for the first alternative than the second
alternative.
The agency believes the proposals may also result in additional
costs, such as the cost of replacing worn or damaged TPMS equipment and
the cost of the time it would take for a driver to react to a low tire
pressure warning by pulling over to a gas station to check and inflate
the vehicle's tires. NHTSA has not attempted to quantify those costs.
II. Background
A. The Transportation Recall Enhancement, Accountability, and
Documentation Act
Congress enacted the Transportation Recall Enhancement,
Accountability, and Documentation (TREAD) Act on November 1, 2000.\3\
Section 13 of the TREAD Act mandates ``a rulemaking for a regulation to
require a warning system in new motor vehicles to indicate to the
operator when a tire is significantly under inflated'' within one year
of the TREAD Act's enactment. Section 13 also provides that the
regulation must take effect within two years of the completion of the
rulemaking.
---------------------------------------------------------------------------
\3\ Public Law 106-414.
---------------------------------------------------------------------------
B. Previous Rulemaking on Tire Pressure Monitoring Systems
NHTSA first considered requiring a ``low tire pressure warning
device'' in 1970. However, the agency determined that only warning
device then available was an in-vehicle indicator, and that its cost
was too high.
During the 1970s, several manufacturers developed inexpensive on-
tire warning devices. In addition, the price of in-vehicle warning
devices dropped significantly.
On January 26, 1981, NHTSA published an Advanced Notice of Proposed
Rulemaking (ANPRM)
[[Page 38984]]
soliciting public comment on whether the agency should propose a new
Federal motor vehicle safety standard requiring each new motor vehicle
to have a low tire pressure warning device which would ``warn the
driver when the tire pressure in any of the vehicle's tires was
significantly below the recommended operating levels.'' (46 FR 8062).
NHTSA noted in the ANPRM that under-inflated tires increase the
rolling resistance of vehicles and, correspondingly, decrease their
fuel economy. Research data at the time indicated that radial tires
under-inflated by 10 pounds per square inch (psi) reduced the fuel
economy of the vehicle on which they were mounted by 3 percent. Because
of the worldwide oil shortages in the late 1970s and early 1980s, NHTSA
was interested in finding ways to increase the fuel economy of
passenger vehicles (i.e., passenger cars and multipurpose passenger
vehicles). Since surveys conducted by the agency showed that about 50
percent of passenger car tires and 13 percent of truck tires were
operated at pressures below the vehicle manufacturers' recommended
inflation levels, the agency believed that low tire pressure warning
devices would encourage drivers to maintain their tires at the proper
inflation level, thus maximizing their vehicles' fuel economy.
Moreover, a 1973 study by Indiana University concluded that under-
inflated tires were a probable cause of 1.4 percent of all motor
vehicle crashes.\4\ Based on that figure, and the approximately 18.3
million motor vehicle crashes then occurring annually in the U.S., the
agency suggested that under-inflated tires were probably responsible
for 260,000 crashes each year (1.4 percent x 18.3 million crashes).
---------------------------------------------------------------------------
\4\ Indiana Tri-Level Study of the Causes of Traffic Accidents,
1973.
---------------------------------------------------------------------------
In the ANPRM, the agency sought answers from the public to several
questions, including:
(1) What tire pressure level should trigger the warning device?
(2) Should the agency specify the type of warning device (i.e., on-
tire, in-vehicle) to be used?
(3) What would it cost to produce and install an on-tire or in-
vehicle warning device?
(4) What is the fuel saving potential of low tire pressure warning
devices?
(5) What studies have been performed which would show cause and
effect relationships between low tire pressure and auto crashes?
(6) What would be the costs and benefits of a program to educate
the public on the benefits of maintaining proper tire pressure?
NHTSA terminated the rulemaking on August 31, 1981. (46 FR 43721,
August 31, 1981). The agency did so because public comments on the
ANPRM indicated that the low tire pressure warning devices available at
the time either had not been proven to be accurate and reliable or were
too expensive. The comments indicated that in-vehicle warning devices
had been proven to be accurate and reliable, but would have had a
retail cost of $200 (in 1981 dollars) per vehicle. NHTSA stated, ``Such
a cost increase cannot be justified by the potential benefits, although
those benefits might be significant.'' (46 FR 43721). The comments also
indicated that on-tire warning devices cost only about $5 (in 1981
dollars) per vehicle, but they had not been developed to the point
where they were accurate and reliable enough to be required. The
comments also suggested that on-tire warning devices were subject to
road hazards, such as scuffing at curbs, ice, mud, etc. However, NHTSA
said that it still believed that ``[m]aintaining proper tire inflation
pressure results in direct savings to drivers in terms of better gas
mileage and longer tire life, as well as offering increased safety.''
(46 FR 43721).
III. Problem Description
Drivers' infrequent monitoring of their vehicles' tire pressure,
combined with the difficulty of visually detecting when a tire is
several psi below the recommended inflation pressure and with typical
tire pressure losses due to natural leakage and seasonal climatic
changes, contribute to many vehicles' having under-inflated tires.
A. Infrequent Consumer Monitoring of Tire Pressure
Surveys have shown that most drivers infrequently check the
inflation pressure in their vehicles' tires. One such survey was the
omnibus survey conducted by the Bureau of Transportation Statistics
(BTS) in September 2000 for NHTSA. The BTS conducted 1,017 household
interviews. One of the questions posed was: ``How often do you, or the
person who checks your tires, check the air pressure in your tires?''
The answers indicated that 29 percent of the respondents stated that
they check the air pressure in their tires monthly; 29 percent stated
that they check the air pressure only when one or more of their
vehicle's tires appears under-inflated; 19 percent stated that they
only have the air pressure checked when the vehicle is serviced; 5
percent stated that they only check the air pressure before taking
their vehicle on a long trip; and 17 percent stated that they check the
air pressure on some other occasion. Thus, 71 percent of drivers stated
that they check the air pressure in their vehicles' tires less than
once a month.\5\
---------------------------------------------------------------------------
\5\ The agency notes that it seems likely that the respondents
overstated the frequency with which they check tire pressure,
particularly given the fact that this survey was conducted during
the height of publicity in the fall of 2000 about tire failures on
sport utility vehicles.
---------------------------------------------------------------------------
In addition, NHTSA's National Center for Statistics and Analysis
(NCSA) conducted a survey in February 2001. The survey was designed to
assess the extent to which passenger vehicle drivers are aware of the
recommended air pressure for their tires, if they monitor air pressure,
and to what extent actual tire pressure differs from that recommended
by the vehicle manufacturer.
Data was collected through the infrastructure of the National
Accident Sampling System--Crashworthiness Data System (NASS-CDS). The
NASS-CDS consists of 24 Primary Sampling Units (PSUs) located across
the country. Within each PSU, a random selection of zip codes was
obtained from a list of eligible zip codes. Within each zip code, a
random selection of two gas stations was obtained.
A total of 11,530 vehicles were inspected at these gas stations.
This total comprised 6,442 passenger cars, 1,874 SUVs, 1,376 vans, and
1,838 pick-up trucks. For analytical purposes, the data were divided
into three categories: (1) passenger cars with P-metric tires; (2)
pick-up trucks, SUVs, and vans with P-metric tires; and (3) pick-up
trucks, SUVs, and vans with either light truck (LT) or flotation tires.
Drivers were asked how often they normally check their tires to
determine if they are properly inflated. Their answers are in the
following table:
[[Page 38985]]
----------------------------------------------------------------------------------------------------------------
Drivers of Drivers of pick-up trucks, SUVs and
passenger cars vans (%)
How often is tire pressure checked? (%) -------------------------------------
------------------- LT or flotation
P-metric tires P-metric tires tires
----------------------------------------------------------------------------------------------------------------
Weekly................................................. 8.76 8.69 8.16
----------------------------------------------------------------------------------------------------------------
Monthly................................................ 21.42 25.19 39.88
----------------------------------------------------------------------------------------------------------------
When they seem low..................................... 25.63 23.58 15.59
----------------------------------------------------------------------------------------------------------------
When serviced.......................................... 30.18 27.72 25.54
----------------------------------------------------------------------------------------------------------------
For long trip.......................................... 0.99 2.39 2.17
----------------------------------------------------------------------------------------------------------------
Other.................................................. 6.46 8.27 6.97
----------------------------------------------------------------------------------------------------------------
Do not check........................................... 6.56 4.16 1.69
----------------------------------------------------------------------------------------------------------------
These data indicate that only about 30 percent of drivers of
passenger cars, 34 percent of drivers of pick-up trucks, SUVs, and vans
with P-metric tires, and 48 percent of drivers of pick-up trucks, SUVs,
and vans with either LT or flotation tires claim that they check the
inflation level in their tires at least once a month.
B. Loss of Tire Pressure Due to Natural and Other Causes
According to data from the tire industry, 85 percent of all tire
air pressure losses are the result of slow leaks that occur over a
period of hours, days, or months. Only 15 percent of tire air pressure
losses are rapid air losses caused by contact with a road hazard, e.g.,
when a tire is punctured by a large nail that does not end up stuck in
the tire. Slow leaks may be caused by many factors. Tires typically
lose air pressure through natural leakage and permeation at a rate of 1
pound per square inch (psi) per month. In addition, seasonal climatic
changes result in air pressure losses on the order of 1 psi for every
10 deg.F decrease in the ambient temperature. Slow leaks also may be
caused by slight damage to a tire, such as a road hazard that punctures
a small hole in the tire or a nail that sticks in the tire. The agency
has no data indicating how often any of these causes results in a slow
leak.
C. Percentage of Motor Vehicles With Under-Inflated Tires
During the tire pressure survey, NASS-CDS crash investigators
measured tire pressure on each vehicle coming into the gas station and
compared the measured pressures to the vehicle manufacturer's
recommended tire pressure. They found that about 36 percent of
passenger cars and about 40 percent of light trucks had at least one
tire that was at least 20 percent below the vehicle manufacturer's
recommended cold inflation pressure. About 26 percent of passenger cars
and 29 percent of light trucks had at least one tire that was at least
25 percent below the vehicle manufacturer's recommended cold inflation
pressure. The agency notes those levels of under-inflation because they
are the threshold levels at which the low tire pressure warning
telltale would have to be illuminated in the two alternatives proposed
in this NPRM.
D. Consequences of Under-Inflation of Tires
1. Reduced Vehicle Safety
When a tire is used while significantly under-inflated, its
sidewalls flex more and the air temperature inside it increases, making
the tire more prone to failure. In addition, a significantly under-
inflated tire loses lateral traction, making handling more difficult.
The agency also has received data from Goodyear indicating that
significantly under-inflated tires increase a vehicle's stopping
distance on wet surfaces.
NHTSA's crash files do not contain any direct evidence that points
to low tire pressure as the cause of any particular crash. However,
this lack of data does not imply that low tire pressure does not cause
or contribute to any crashes. It simply reflects the fact that
measurements of tire pressure are not among the vehicle information
included in the crash reports received by the agency and placed in its
crash data bases.\6\
---------------------------------------------------------------------------
\6\ These crash data bases are the National Automotive Sampling
System--Crashworthiness Data System (NASS-CDS) and the Fatality
Analysis Reporting System (FARS).
---------------------------------------------------------------------------
The only tire-related data element in the agency's data bases is
``flat tire or blowout.'' Even in crashes for which a flat tire or
blowout is reported, crash investigators cannot tell whether low tire
pressure contributed to the tire failure.
The agency examined its crash files to gather information on tire-
related problems that resulted in crashes. The National Automotive
Sampling System--Crashworthiness Data System (NASS-CDS) has trained
investigators who collect data on a sample of tow-away crashes around
the United States. These data can be weighted to generate national
estimates.
The NASS-CDS General Vehicle Form contains a value indicating
vehicle loss of control due to a blow out or flat tire. This value is
used only when a vehicle's tire went flat, causing a loss of control of
the vehicle and a crash. The value is not used for cases in which one
or more of a vehicle's tires was under-inflated, preventing the vehicle
from performing as well as it could have in an emergency situation.
NHTSA examined NASS-CDS data for 1995 through 1998 and estimated
that 23,464 tow-away crashes, or one-half of one percent of all
crashes, are caused by blowouts or flat tires each year. This is
significantly fewer crashes than estimated by the 1973 Indiana Tri-
Level study. However, the 260,000 crashes estimated in that study
represented all crashes in which under-inflation was a probable or
possible cause. The 23,464 crashes estimated from the NASS-CDS data are
tow-away crashes caused by tire failure only. Further, in 1977, only 12
percent of vehicles were equipped with radial tires, while today over
90 percent of vehicles are equipped with radial tires. Radial tires are
much more structurally sound than the bias-ply tires that were widely
used in 1977. Thus, the current estimate of 23,464 crashes and the 1977
estimate of 260,000 crashes are not comparable.
[[Page 38986]]
The agency placed the tow-away crashes from the NASS-CDS files into
two categories: Passenger car crashes and light truck crashes.
Passenger cars were involved in 10,170 of the tow-away crashes caused
by blowouts or flat tires, and light trucks were involved in the other
13,294.
NHTSA also examined data from the Fatality Analysis Reporting
System (FARS) for evidence of tire problems involved in fatal crashes.
In FARS, if tire problems are noted after the crash, the simple fact of
their existence is all that is noted. No attempt is made to ascribe a
role in the crash to those problems. Thus, the agency does not know
whether the noted tire problem caused the crash, influenced the
severity of the crash, or simply occurred during the crash. For
example, a tire may have blown out and caused the crash, or a tire may
have blown out during the crash when the vehicle struck some object
such as a curb.
Thus, while an indication of a tire problem in the FARS file gives
some clue as to the potential magnitude of tire problems in fatal
crashes, the FARS data cannot give a precise measure of the causal role
played by those problems. The very existence of tire problems are
sometimes difficult to detect and to code accurately. Further, coding
practices vary from State to State. Nevertheless, the agency notes
that, from 1995 to 1998, 1.10% of all light vehicles involved in fatal
crashes were coded as having tire problems. Over 535 fatal crashes
involved vehicles coded with tire problems.
Under-inflated tires can contribute to other types of crashes than
those resulting from blow outs or tire failure, including crashes which
result from: an increase in stopping distance; skidding and/or a loss
of control of the vehicle in a curve or in a lane change maneuver; or
hydroplaning on a wet surface. However, the agency does not have any
data on how often under-inflated tires cause crashes or contribute to
their occurrence.
Tires are designed to perform at a specific inflation pressure.
When a tire is under-inflated, the shape of its footprint and the
pressure it exerts on the road surface are both altered. One
consequence of this alteration can be a reduction in the tire's ability
to transmit (or generate) braking force to the road surface, at least
on wet surfaces.\7\ Thus, under-inflated tires may increase a vehicle's
stopping distance on wet surfaces. This is discussed more fully in the
Benefits section below.
---------------------------------------------------------------------------
\7\ On dry surfaces, stopping distance seems to be only mildly
affected by inflation pressure. Thomas D. Gillespie, Fundamentals of
Vehicle Dynamics, Society of Automotive Engineers, 1992, p. 57.
---------------------------------------------------------------------------
2. Reduced Tread Life
Unpublished data submitted by Goodyear indicate that when a tire is
under-inflated, more pressure is placed on the shoulders of the tire,
causing the tread to wear incorrectly. The Goodyear data also indicated
that the tread on an under-inflated tire wears more rapidly than it
would if the tire were inflated to the proper pressure. The agency
requests comment on this issue.
The Goodyear data indicate that the average tread life of a tire is
45,000 miles, and the average cost of a tire is $61 (in 2000 dollars).
Goodyear also estimated that a tire's average tread life would drop to
68 percent of the expected tread life if tire pressure dropped from 35
psi to 17 psi and remained there. Goodyear also assumed that this
relationship was linear. Thus, for every 1 psi drop in tire pressure,
tread life would decrease by 1.78 percent (32 percent/18). This loss of
tread life would take place over the lifetime of the tire. Thus,
according to Goodyear's data, if the tire remained under-inflated by 1
psi over its lifetime, its tread life would decrease by about 800 miles
(1.78 percent of 45,000 miles).
As noted above, data from the NCSA tire pressure survey show that
36 percent of passenger cars had at least one tire that was under-
inflated by at least 20 percent. The average level of under-inflation
of the four tires on these cars was 6.1 psi. Thus, on average,
passenger cars could lose about 4,880 miles (6.1 psi x 800 miles) of
tire life due to under-inflation, if their tires were under-inflated to
that extent throughout the life of the tires.
As also noted above, data from the NCSA tire pressure survey also
show that about 40 percent of light trucks had at least one tire that
was under-inflated by at least 20 percent. The average level of under-
inflation of the four tires on these light trucks was 7.7 psi. Thus, on
average, those light trucks could lose about 6,160 miles (7.7 psi x
800 miles) of tire life due to under-inflation, if their tires were
under-inflated to that extent throughout the life of the tires.
3. Reduced Fuel Economy
Under-inflated tires increase the rolling resistance of vehicles
and, correspondingly, decrease their fuel economy. According to a 1978
report,\8\ fuel efficiency is reduced by one percent for every 3.3 psi
of under-inflation. More recent data provided by Goodyear indicate that
fuel efficiency is reduced by one percent for every 2.96 psi of under-
inflation.
---------------------------------------------------------------------------
\8\ The Aerospace Corporation, Evaluation of Techniques for
Reducing In-use Automotive Fuel Consumption, June 1978.
---------------------------------------------------------------------------
NHTSA notes that there is an apparent conflict between the Goodyear
data indicating under-inflated tires increase a vehicle's stopping
distance and the data indicating under-inflated tires increase a
vehicle's rolling resistance. Since an under-inflated tire typically
has a larger tread surface area (i.e., tire footprint) in contact with
the road, the vehicle should have more traction, and its stopping
distance should be reduced.
The larger footprint does result in an increase in rolling
resistance on dry road surfaces due to increased friction between the
tire and the road surface. However, the larger tire footprint also
reduces the tire load per unit area. On dry road surfaces, the
countervailing effects of a larger footprint and reduced load per unit
of area nearly offset each other, with the result that the vehicle's
stopping distance performance is only mildly affected by under-
inflation.
On wet surfaces, however, under-inflation typically increases
stopping distance for several reasons. First, as noted above, the
larger tire footprint provides less tire load per area than a smaller
footprint. Second, since the limits of adhesion are lower and achieved
earlier on a wet surface than on a dry surface, a tire with a larger
footprint, given the same load, is likely to slide earlier than the
same tire with a smaller footprint because of the lower load per
footprint area. The rolling resistance of an under-inflated tire on a
wet surface is greater than the rolling resistance of the same tire
properly-inflated on the same wet surface. This is because the slightly
larger tire footprint on the under-inflated tire results in more rubber
on the road and hence more friction to overcome. However, the rolling
resistance of an under-inflated tire on a wet surface is less than the
rolling resistance of the same under-inflated tire on a dry surface
because of the reduced friction caused by the thin film of water
between the tire and the road surface. The less tire load per area and
lower limits of adhesion of an under-inflated tire on a wet surface are
enough to overcome the increased friction caused by the larger
footprint of the under-inflated tire. Hence, under-inflated tires cause
longer stopping distance on wet surfaces than properly-inflated tires.
IV. Tire Pressure Monitoring Systems
There are two types of tire pressure monitoring systems (TPMSs).
Direct systems directly measure the pressure in
[[Page 38987]]
a vehicle's tires, while indirect ones estimate the pressure. Both
types inform the driver when the pressure in one or more tires falls
below a pre-determined level. Unless the TPMS is connected to an
automatic inflation system, the driver must stop the vehicle and
inflate the under-inflated tire(s), preferably to the pressure
recommended by the vehicle manufacturer. Currently, TPMSs are available
as original equipment on a few vehicle models. They are available also
as after-market equipment, but few are sold.
NHTSA's Vehicle Research and Test Center (VRTC) evaluated six
direct and four indirect TPMSs that are currently available.\9\ The
VRTC found that the direct TPMSs were accurate to within an average of
1.0 psi, and indirect systems were accurate to within an
average of 1.1 psi.\10\ This leads the agency to believe
that current TPMSs are more accurate than the systems that were
available at the time of the agency's 1981 rulemaking on TPMSs.
---------------------------------------------------------------------------
\9\ An Evaluation of Existing Tire Pressure Monitoring Systems,
May 2001. A copy of this report is available in the docket.
\10\ This is not to say that the systems were able to detect a
1.0 psi drop in pressure. The systems were accurate within
1.0 to 1.1 psi once tire pressure had fallen by a
certain percentage.
---------------------------------------------------------------------------
Following is a description of the two types of TPMSs and their
advantages and disadvantages.
A. Indirect TPMSs
Indirect TPMSs typically work with the vehicle's anti-lock brake
system (ABS). The ABS employs wheel speed sensors to measure the
rotational speed of each of the four wheels. As a tire's pressure
decreases, the rolling radius decreases, and the rotational speed of
that wheel increases correspondingly. Most indirect TPMSs compare each
wheel's rotational speed with the rotational speed of the other wheels.
If one tire becomes significantly under-inflated while the others
remain at the proper pressure, the indirect TPMS can detect it because
that wheel's rotational speed is higher than the rotational speed of
the other wheels. This information is conveyed to the driver by a
simple telltale. The telltale indicates that a tire is under-inflated,
but cannot identify which tire is under-inflated. Current vehicles that
have indirect systems include the Toyota Sienna, Ford Windstar, and
Oldsmobile Alero.
B. Direct TPMSs
Direct TPMSs use pressure sensors, located in each wheel, to
directly measure the pressure in each tire. These sensors broadcast
data via a wireless radio frequency transmitter to a central receiver
which analyzes the data. The central receiver is connected to a display
mounted inside the vehicle. The type of display varies from a simple,
single telltale to a display showing the pressure and temperature in
each tire, sometimes including the spare tire. Thus, direct TPMSs can
be linked to a display that tells the driver which tire is under-
inflated. An example of a vehicle equipped with a direct system is the
Chevrolet Corvette.
C. Advantages and Disadvantages
1. Indirect TPMSs
Indirect TPMSs have several advantages. First, they are less
expensive than direct TPMSs for vehicles already equipped with an ABS.
If a vehicle is already equipped with an ABS, the vehicle's
manufacturer will only have to add the capability to monitor the wheel
speed sensors, a low tire pressure warning telltale, and a reset
button, and make some software changes. Making these additions and
changes in a way that produces indirect systems like those currently on
motor vehicles would cost about $12.90 per vehicle. However, as
explained below, the agency is uncertain whether such an indirect TPMS
would comply with either of the alternatives proposed in this NPRM.
NHTSA tested four current ABS-based indirect TPMSs. None of the
four met the proposed requirements for either alternative. These TPMSs
had problems detecting two significantly under-inflated tires on the
same axle and on the same side of the vehicle. They also did not
illuminate the low tire pressure warning telltale when the pressure in
the vehicle's tires decreased to 20 percent, or even 25 percent, below
the vehicle manufacturer's recommended cold inflation pressure. NHTSA
does not know whether improving current indirect TPMSs to meet the
requirements of either alternative would result in additional costs.
The agency requests comments on this issue.
Pickup trucks comprise about 40 percent of light truck sales. Some
percentage of pickup trucks that have ABS have only one wheel speed
sensor for the rear axle. In order to meet the requirements of either
proposed alternative, NHTSA believes vehicle manufacturers would have
to add a fourth wheel speed sensor to these trucks at an estimated cost
of $20 per vehicle. The agency assumes for this analysis that about 10
percent of all light trucks, or 7.5 percent of all light vehicles with
ABS, would be in this category. However, the agency requests comment on
the percentage of pickup trucks that would need this modification.
For vehicles currently without ABS, there are two indirect
measurement choices. First, the vehicle manufacturer could add ABS and
the necessary TPMS features to the vehicle. NHTSA estimates that this
would cost about $240 per vehicle. The agency does not expect
manufacturers to make this choice unless they are already planning for
other reasons to add ABS. Second, the vehicle manufacturer could add
wheel speed sensors and the necessary TPMS features to the vehicle.
NHTSA estimates that this approach would cost about $130 per vehicle.
Second, the wheel components of indirect TPMSs are more robust and
less likely to sustain damage than the wheel components of direct
TPMSs. The wheel speed sensors of indirect TPMSs are located behind the
brakes and often are integrated into the wheel hub assembly. This
generally shields them from road damage. In addition, the entire brake/
hub assembly would rarely be removed. In contrast, the pressure sensors
of direct TPMSs are located inside the tire/wheel cavity, potentially
subjecting them to road damage. These sensors also may be subject to
damage during tire maintenance, i.e., rotating or changing the tires.
Finally, indirect TPMSs do not need an independent power source.
They are powered by the car's battery.
Indirect TPMSs also have several disadvantages. First, since most
indirect TPMSs calculate tire pressure by comparing the wheel speeds,
they cannot detect the loss of pressure if all four tires lose pressure
at similar rates. In its evaluation of four indirect TPMSs, the VRTC
found that none of them were able to detect when all four of the
vehicle's tires were equally under-inflated. The VRTC also found that
none of the indirect TPMSs were able to detect when two tires on the
same axle or two tires on the same side of the vehicle were equally
under-inflated.
Second, most indirect TPMSs cannot detect small pressure losses.
The VRTC found that since reductions in tire diameter with reductions
in pressure are very slight in the 15-40 psi range, most indirect TPMSs
require a 20 to 30 percent drop in pressure before they are able to
detect under-inflation. The VRTC also found that those thresholds were
highly dependent on tire and loading factors.
Third, vehicles must be moving for indirect TPMSs to detect an
under-inflated tire. Thus, if a vehicle's tire is already under-
inflated when a person gets in and begins to drive that vehicle, an
indirect TPMS will not be able to
[[Page 38988]]
alert the driver until after the vehicle begins moving.
Fourth, most indirect TPMSs need substantial time to calibrate the
system, i.e., to ``learn'' the variables associated with distinct tire
types under varying driving conditions. The VRTC found that the four
indirect TPMSs it evaluated took anywhere from several minutes to
several hours to calibrate. Calibration is necessary when a vehicle is
first driven. Recalibration is necessary when the pressure in a tire is
changed and when the tires are rotated or replaced. Indirect TPMSs do
not indicate that the system is in calibration mode. During the
calibration mode, the system is not monitoring tire pressure. Thus, if
one or more tires becomes significantly under-inflated while the system
is calibrating, the driver would not be alerted. Moreover, the agency
notes that the calibration process is prone to human error. For
example, a driver may accidentally press the reset button when one or
more of the vehicle's tires is under-inflated, but not under-inflated
enough to illuminate the low tire pressure warning telltale. This would
re-calibrate the system so that it accepts the under-inflated condition
as normal. The indirect TPMS then would not be able to detect an under-
inflated tire until one or more tires was even more under-inflated than
it already was. The agency requests comments specifically addressing
the issue of human error that may occur with indirect TPMSs.
Fifth, apart from the time needed to calibrate, indirect TPMSs also
need several minutes to detect an under-inflated tire. The VRTC found
that the four indirect TPMSs it evaluated took one to ten minutes to
detect an under-inflated tire.
Sixth, indirect TPMSs cannot tell the driver which tire is under-
inflated.
Seventh, indirect TPMSs sometimes incorrectly indicate that a
vehicle has an under-inflated tire when the vehicle is being driven on
gravel or bumpy roads, is being driven at high speeds, e.g., over 70
mph, or has mismatched tires or a tire that is out of balance or out of
alignment.
2. Direct TPMSs
Direct TPMSs have several advantages. First, since direct TPMSs
actually measure the pressure in each tire, they are able to detect
when any tire or combination of tires is under-inflated, including when
all four of the vehicle's tires are equally under-inflated.
Second, since most direct TPMSs are battery-operated, they can
operate while the vehicle is stationary. Thus, if a vehicle's tire
becomes significantly under-inflated while the vehicle is parked, a
direct TPMS can alert the driver as soon as he or she starts the
vehicle.
Third, direct TPMSs can detect small pressure losses. Some systems
can detect a drop in pressure as small as 1 psi.
Fourth, direct TPMSs can be linked to a display that tells the
driver which tire is under-inflated and the actual pressure in each
tire.
Fifth, direct TPMSs will not give false positives if the vehicle is
being driven on gravel or bumpy roads, or has mismatched tires or a
tire that is out of balance or out of alignment.
Direct TPMSs also have disadvantages. First, they are more
expensive than indirect TPMSs for vehicles already equipped with ABS.
There are two main costs associated with direct TPMSs: sensors and a
receiver. There is a wide disparity in costs for sensors, depending on
what type of information is sensed.\11\ Providing only pressure
sensors, as proposed to be required by both alternatives proposed in
this NPRM, would cost from $5 to $10 per wheel, or $20 to $40 per
vehicle.
---------------------------------------------------------------------------
\11\ For example, some sensors sense temperature in addition to
pressure.
---------------------------------------------------------------------------
The costs associated with a receiver depend upon whether the
vehicle already has a receiver capable of receiving and processing the
information coming from the sensors. NHTSA estimates that about 60
percent of vehicles currently have such a receiver. Making some
software changes and adding a display showing the pressure for each
tire would cost about $25 per vehicle. The 40 percent of vehicles
without such a receiver would have to be equipped with a receiver
incorporating the necessary software and with the display. The agency
estimates that this would cost about $40 to $50 per vehicle.
The agency estimates that the total cost of adding a direct TPMS to
a vehicle that is already equipped with a receiver would be $49 to
$69.\12\ For a vehicle that is not already equipped with a receiver,
the cost would be $64 to $94. This is more than the cost of adding an
indirect TPMS to a vehicle already equipped with an ABS, but less than
the cost of adding wheel speed sensors or an ABS and an indirect TPMS
to a vehicle not already equipped with an ABS.
---------------------------------------------------------------------------
\12\ These figures include about $4 per vehicle for the cost of
actually installing the direct TPMS.
---------------------------------------------------------------------------
Second, the wheel components of direct TPMSs are less robust and
more likely to sustain damage than the wheel components of indirect
TPMSs, especially when tires are taken off the rim. This issue is
discussed above in the section on the advantages of indirect TPMSs. The
agency notes, however, that it has not received any information
indicating that direct TPMSs have sustained damage during driving or
tire maintenance. The agency requests comments on the likelihood of
such damage.
Third, most direct TPMSs need an independent power source. Those
that do are powered by batteries, which generally have a life span of
five to ten years. This also means that unless a direct TPMS is
equipped with a low battery warning indicator, the driver might not
know when the batteries for a direct TPMS have expired.
Finally, most direct TPMSs must be reset after a vehicle's tires
are replaced. When a vehicle's tires are rotated, most direct TPMSs
require that the sensor locations be reassigned in the receiver.
3. Tabular Summary of Advantages and Disadvantages of Indirect and
Direct TPMSs
Advantages and Disadvantages of Indirect and Direct TPMSs
------------------------------------------------------------------------
Indirect TPMSs Direct TPMSs
------------------------------------------------------------------------
Cost of adding to vehicle $12.90.............. $79.
with ABS, but without
receiver.
------------------------------------------------------------------------
Cost of adding to vehicle $12.90.............. 59.
with ABS and receiver.
------------------------------------------------------------------------
Cost of adding to vehicle $130 for wheel speed 79.
without ABS or receiver. sensors; $240 for
ABS.
------------------------------------------------------------------------
[[Page 38989]]
Cost of adding to vehicle $130 for wheel speed 59.
without ABS, but with sensors; $240 for
receiver. ABS.
------------------------------------------------------------------------
Susceptibility of wheel Less likely......... More likely.
components to damage during
tire installation and
removal.
------------------------------------------------------------------------
Need for an independent No.................. Yes.
power source.
------------------------------------------------------------------------
Need to reset after a Yes, system must be Yes.
vehicle's tires are re-calibrated.
replaced or rotated.
------------------------------------------------------------------------
Ability to detect loss of No.................. Yes.
air pressure if all four
tires lose pressure.
------------------------------------------------------------------------
Ability to detect small No.................. Yes.
pressure losses.
------------------------------------------------------------------------
Ability to detect under- No, vehicle must be Yes.
inflated tire while vehicle moving.
is stationary.
------------------------------------------------------------------------
Ability to identify which No.................. Yes.
tire is under-inflated.
------------------------------------------------------------------------
Susceptible to giving false Yes, if the vehicle No.
indications of a is being driven on
significantly under- gravel or bumpy
inflated tire. roads or at high
speeds (70 mph) or if it
has mismatched
tires or a tire out
of balance or a out
of alignment.
------------------------------------------------------------------------
V. Agency Proposal
A. Summary of Proposal
The agency is proposing two alternative versions of the TPMS
standard. Both alternatives would require passenger cars, multipurpose
passenger vehicles, trucks, and buses with a gross vehicle weight
rating of 4,536 kilograms (10,000 pounds) or less, manufactured on or
after November 1, 2003, to be equipped with a TPMS and a low tire
pressure warning telltale (yellow) to alert the driver that one or more
of the vehicle's tires is significantly under-inflated. Both
alternatives would require the TPMS in each vehicle to be compatible
with all replacement or optional tire sizes/rims recommended for that
vehicle by the vehicle manufacturer. Both alternatives would require
vehicle manufacturers to provide written instructions, in the owner's
manual if one is provided, explaining the purpose of the low tire
pressure warning telltale, the potential consequences of significantly
under-inflated tires, and what actions drivers should take when the low
tire pressure warning telltale is illuminated.
The first alternative would define ``significantly under-inflated''
as the tire pressure 20 percent or more below the vehicle
manufacturer's recommended cold inflation pressure for the vehicle's
tires, or an absolute level of pressure to be specified in the new
standard, whichever pressure is higher. It would require the low tire
pressure warning telltale to illuminate within 10 minutes of driving
after any tire or combination of tires on the vehicle becomes
significantly under-inflated. It would require the low tire pressure
warning telltale to remain illuminated as long as any of the vehicle's
tires remains significantly under-inflated, and the ignition switch is
in the ``on'' (``run'') position. It would require that the telltale be
deactivatable, manually or automatically, only when the vehicle no
longer has a tire that is significantly under-inflated.
The second alternative would define ``significantly under-
inflated'' as the tire pressure 25 percent below the vehicle
manufacturer's recommended cold inflation pressure for the vehicle's
tires, or an absolute level of pressure to be specified in the new
standard, whichever pressure is higher. The absolute pressure levels
would be the same for both proposals. The second alternative would
require the low tire pressure warning telltale to illuminate within 10
minutes of driving after any tire or combination of tires, up to a
total of three tires, becomes significantly under-inflated. Like the
first alternative, the second alternative would require the low tire
pressure warning telltale to remain illuminated as long as any of the
vehicle's tires remains significantly under-inflated, and the ignition
switch is in the ``on'' (``run'') position. The second alternative also
would require that the telltale be deactivatable, manually or
automatically, only when the vehicle no longer has a tire that is
significantly under-inflated.
The agency believes that only direct TPMSs will be able to meet the
requirements of the first alternative. Current indirect TPMSs typically
cannot detect significant under-inflation until the pressure in one of
the vehicle's tires is about 30 percent below the pressure in at least
some of the other tires. Further, they cannot detect when all four
tires lose pressure at the same time.
NHTSA believes that direct TPMSs and upgraded indirect TPMSs will
be able to meet the requirements of the second alternative. The agency
requests comments on whether this goal is practicable.
B. Vehicles Covered by This Proposal
NHTSA is proposing to require TPMSs on passenger cars, multipurpose
passenger vehicles, trucks, and buses with a gross vehicle weight
rating of 4,536 kilograms (10,000 pounds) or less.
NHTSA is not proposing to require TPMSs on motorcycles because,
unlike the types of vehicles that would be subject to the proposed
standard on TPMS, motorcycles use tubed tires. In order for a direct
TPMS to work with tubed tires, the pressure sensor would not only have
to be inside the tire, but also inside the tube itself. The agency is
not aware of any TPMSs that are made to work with tubed tires.
NHTSA is also not proposing to require TPMSs on medium (10,001-
26,000 lbs. GVWR) and heavy (greater than 26,001 lbs. GVWR) vehicles
for several reasons. First, this rulemaking is required by the TREAD
Act, which was passed in response to the Firestone recall.\13\ Since
that recall was limited to light vehicles, the agency has limited its
study of under-inflation to light vehicles.
---------------------------------------------------------------------------
\13\ On August 9, 2000, Firestone announced that it was
recalling 14.4 million ATX, ATX II, and Wilderness tires after
receiving scores of complaints alleging that the tread on these
tires was separating. NHTSA is investigating these tires and has
attributed 203 deaths and more than 700 injuries to crashes
involving tread separations on these tires.
---------------------------------------------------------------------------
[[Page 38990]]
Second, the issues associated with under-inflated tires on medium
and heavy vehicles are different from and more complex than the issues
associated with under-inflated tires on light vehicles. For example,
medium and heavy vehicles are equipped with tires that are much larger
and have much higher pressure levels than the tires used on light
vehicles. In addition, medium and heavy vehicles are generally equipped
with more axles and tires than light vehicles. Since the TREAD Act
imposed a one-year deadline on this rulemaking, the agency did not have
the time to study and analyze those issues sufficiently.
Third, the Federal Motor Carrier Safety Administration (FMCSA) has
a program that is addressing tire maintenance issues on heavy, but not
medium, vehicles. The FMCSA plans to conduct a comprehensive study,
including possible fleet evaluations of different systems, of all the
issues related to improvement of heavy vehicle tire maintenance.
NHTSA plans to coordinate with the FMCSA to address the issues
associated with heavy vehicle tire maintenance. NHTSA will work with
the FMCSA in examining the desirability of proposing a TPMS standard
for heavy vehicles. The agency will also consider the implications of
those results of that examination for medium vehicles.
C. Definition of ``Significantly Under-Inflated''
Before issuing this notice of proposed rulemaking, NHTSA employees
attended numerous meetings with both tire and vehicle manufacturers to
discuss TPMSs and how the term ``significantly under-inflated'' should
be defined. The agency notes that there is a fundamental disagreement
between vehicle and tire manufacturers as to what constitutes
significant under-inflation.
In general, the tire manufacturers believe that ``significantly
under-inflated'' should be defined as any pressure below the minimum
pressure specified by the tire industry's standard-setting bodies for a
vehicle's gross vehicle weight rating (GVWR) or gross axle weight
rating (GAWR). They argue that any tire with an inflation pressure
below the pressure specified by those bodies as necessary to carry the
vehicle's GVWR or GAWR creates a potential safety problem. They are
concerned that tires with a pressure even 1 psi below this level will
experience increased temperatures and be more likely to fail.
The vehicle manufacturers would like the agency to leave the
definition of ``significant under-inflation'' to them. They argue that
there are too many vehicle-tire-load combinations for the agency to set
one standard, and that the vehicle manufacturers can best determine at
what inflation pressure a particular tire on a particular vehicle is
significantly under-inflated. They suggest that the agency give them
the flexibility to determine the level of significant under-inflation
for the tires on each vehicle.
NHTSA believes that the tire manufacturers' definition is overly
strict. Most manufacturers of light vehicles incorporate some reserve
when determining a tire's recommended cold inflation pressure. Thus,
the pressure in a tire may fall below that recommended pressure without
significantly affecting the safety of the tire.
In addition, the pressures assigned by the tire industry's
standard-setting bodies are simply the result of a mathematical
calculation that a tire enclosing a given volume of air should be able
to carry a certain load. The formula underlying the calculation is
decades old. It remains unchanged even though tire technology and
construction have changed significantly. A given size of today's tires
is more able than the same size of tires 50 or even 25 years ago to
carry a load safely. Thus, the tire industry's calculation is a very
conservative estimate of the load-carrying capability of today's tires.
NHTSA also does not agree with the vehicle manufacturers'
definition. The agency believes that it must set a minimum level to
ensure that tires are not operated at pressures the agency believes are
too low. The agency is proposing a minimum performance standard. Either
proposed alternative would give vehicle manufacturers the freedom to
raise the bar. In this case, either alternative would allow them to
design TPMSs so that they provide a warning before any tire experiences
the amount of pressure loss permitted under the agency proposal. The
agency also believes that a minimum performance standard specifying a
quantified requirement can work for the various vehicle-tire-load
combinations.
NHTSA is proposing two alternative definitions of ``significantly
under-inflated.'' The first would define ``significantly under-
inflated'' as a tire pressure in one, two, three or four tires that is
20 percent or more below the vehicle manufacturer's recommended cold
inflation pressure for the vehicle's tires, or a minimum level of
pressure to be specified in the new standard, whichever pressure is
higher. The second would define ``significantly under-inflated'' as a
tire pressure in one, two, or three tires that is 25 percent or more
below the vehicle manufacturer's recommended cold inflation pressure
for the vehicle's tires, or a minimum level of pressure to be specified
in the new standard, whichever pressure is higher.
In selecting these figures, NHTSA considered several factors.
First, there is no bright line at the loss of air pressure definitely
becomes a safety issue. Second, we did not wish to select a level of
pressure loss so low that the warning telltale illuminates so often
that it becomes a nuisance. Drivers could end up ignoring such a
telltale altogether. Accordingly, we did not want to select a level as
low as 10 percent below the manufacturer's recommended pressure. Our
assessment of current TPMSs leads us to conclude that detecting 20
percent under-inflation is feasible for direct TPMSs, but may not be
feasible for indirect ones. Most current indirect TPMSs are not able to
detect differences in inflation pressure among a vehicle's tires that
are less than 30 percent. However, we believe that indirect TPMSs can
be improved sufficiently to enable them to detect 25 percent
differentials. We are asking for comments on these figures. To aid the
agency in selecting a figure for the final rule, NHTSA requests any
data or analysis relating to the safety implications of under-inflation
within the range of under-inflation discussed in this paragraph. It
also requests information regarding the practicability of designing and
manufacturing such systems.
The agency has data indicating that, as the amount of under-
inflation increases, so does the negative effect on the vehicle's
braking performance, fuel economy, and tire life. For example,
according to data from Goodyear, a vehicle traveling at 62 mph on a wet
surface (0.05 inch of water on the road) takes about 442 feet to stop
if all of its tires are properly inflated. If all of its tires are
under-inflated by 20 percent, the vehicle takes about 462 feet to stop.
If all of its tires are under-inflated by 25 percent, the vehicle takes
almost 470 feet to stop. The effects of 20 percent and 25 percent
under-inflation on a vehicle's fuel economy and tire life are detailed
in the Benefits section below.
The agency notes that, in some cases, sole reliance on the 20
percent or 25 percent figure would yield inflation pressures below 140
kPa (20 psi), a pressure at which the agency believes safety may become
an issue. For example, the lowest vehicle manufacturer's recommended
cold inflation pressure known to the agency is 26 psi. Under the second
alternative,
[[Page 38991]]
the low tire pressure warning telltale would not have to illuminate
until one, two or three tires reaches 19.5 psi because 25 percent below
26 psi is 19.5 psi.
To prevent that from occurring, the agency is proposing to
establish a floor. Both the 20 percent figure and the 25 percent figure
are coupled with absolute minimum inflation pressures for the different
types of tires. The warning telltale would have to be illuminated when
the pressure falls to either 20 percent (first alternative) or 25
percent (second alternative) below the vehicle manufacturer's
recommended cold inflation pressure, or the specified absolute minimum
inflation pressure, whichever pressure is higher. These absolute
minimum inflation pressures are specified in the 3rd column of Table 1
(below). (Note: The practical consequences of this floor under the
second alternative is that manufacturers may not be able to use
indirect TPMSs on vehicles for which the manufacturer's recommended
pressure is 27 psi or less. This is because those systems may not be
able to detect pressure differentials of less than 25 percent.)
Most passenger cars, minivans and SUVs are equipped with Standard
Load P-metric tires. NHTSA chose 140 kPa (20 psi) as the minimum
inflation pressure for such tires based on recent testing the agency
conducted. The agency ran a variety of Standard Load P-metric tires at
20 psi with a load for 90 minutes on a dynamometer. None of these tires
failed. This leads the agency to believe that warnings provided above
that level will allow consumers to re-inflate their tires before the
tire fails.
140 kPa is about 58 percent of the maximum inflation pressure for
Standard Load P-metric tires of 240 kPa. The agency calculated the
minimum inflation pressures for the other listed tire types by
multiplying their maximum inflation pressures by 58 percent.
The proposed absolute minimum pressure levels for each type of tire
are set forth in the following table:
Table 1.--Low Tire Pressure Warning Telltale--Minimum Activation Pressure
----------------------------------------------------------------------------------------------------------------
Maximum inflation pressure Minimum activation
------------------------------------------------ pressure
Tire type -------------------------
(kPa) (psi) (kPa) (psi)
----------------------------------------------------------------------------------------------------------------
P-metric--Standard Load............... 240,.................. 35,................... 140 20
300, or............... 44, or................ 140 20
350................... 51.................... 140 20
----------------------------------------------------------------------------------------------------------------
P-metric--Extra Load.................. 280 or................ 41 or................. 160 23
340................... 49.................... 160 23
----------------------------------------------------------------------------------------------------------------
Load Range C.......................... 350................... 51.................... 200 29
----------------------------------------------------------------------------------------------------------------
Load Range D.......................... 450................... 65.................... 260 38
----------------------------------------------------------------------------------------------------------------
Load Range E.......................... 600................... 87.................... 350 51
----------------------------------------------------------------------------------------------------------------
D. Low Tire Pressure Warning Telltale
1. Color
NHTSA is proposing to amend Standard No. 101, Controls and
Displays, 49 CFR Sec. 571.101, to require that the warning telltale be
yellow. The agency believes that yellow is appropriate because it
conveys the message that the driver can continue driving, but should
have the tire pressure checked at the earliest opportunity. Red
represents a high level of urgency. It is used for a warning that a
vehicle system needs immediate attention, and that it is unsafe to
drive the vehicle farther. The agency believes that a driver needs to
attend to a significantly under-inflated tire, but does not need to
stop driving immediately.
2. Symbol
NHTSA is proposing that the warning telltale be identified by one
of the symbols shown below. The first symbol was developed by the
International Organization for Standardization (ISO), and is currently
used in some TPMSs. However, during its May 2001 evaluation of existing
TPMSs, NHTSA received some negative comments from evaluators regarding
the recognizability of this symbol.\14\ As a result, the agency
conducted comprehension tests to determine which symbol best conveyed a
tire pressure problem to drivers. The agency asked 120 people to look
at a picture of 15 symbols, including the ISO symbol, and fill in the
blank in the following statement: ``This image has just appeared on
your vehicle's dashboard. It is a warning for ______.''
---------------------------------------------------------------------------
\14\ An Evaluation of Existing Tire Pressure Monitoring Systems,
May 2001. A copy of this report is available in the docket.
---------------------------------------------------------------------------
Results of this test showed that the ISO symbol was the least
understood among the 15 symbols, with a comprehension rate of only 38%.
However, the agency is proposing it as a possible choice because that
symbol is currently used in most vehicles equipped with a TPMS. Several
of the alternative symbols were recognized 100% of the time. The second
proposed symbol below is one of those. Based on comments on this NPRM,
the agency will select one of those two symbols and require its use
with the telltale.
The third is a symbol that must be used if a vehicle manufacturer
provides a display that identifies which tire is significantly under-
inflated. The agency notes that many vehicles already have an image of
the vehicle built into the dashboard, with lamps located around the
image that illuminate when there is a problem (e.g., an incompletely
closed door) in that area. Thus, the agency is proposing this symbol in
addition to the first two symbols.
The three proposed symbols are below:
BILLING CODE 4910-59-P
[[Page 38992]]
[GRAPHIC] [TIFF OMITTED] TP26JY01.000
BILLING CODE 4910-59-C
[[Page 38993]]
3. Time Frame for Telltale Illumination
As noted above, according to data from the tire industry and
consumer surveys, 85 percent of tire pressure losses are slow pressure
losses. These are losses in which it takes anywhere from several
minutes to several weeks for the tire to become significantly under-
inflated. The other 15 percent of tire pressure losses are rapid
pressure losses. These losses typically result from a tire's being
punctured (without the puncturing object's becoming embedded in the
tire) or ruptured. TPMSs are designed to alert the driver to slow
pressure losses. They are not intended to alert the driver to a rapid
pressure loss.
The agency has received data from TPMS manufacturers indicating
that direct TPMSs can alert the driver in less than one minute after a
tire becomes significantly under-inflated, while indirect TPMSs can
take up to ten minutes to do so. Since TPMSs are designed to alert the
driver to slow pressure losses only, the agency believes that ten
minutes is ample time. The agency believes that a TPMS that alerts the
driver within ten minutes after a tire reaches the significant under-
inflation threshold pressure would provide the driver sufficient time
to take corrective action and avoid serious tire degradation. Thus, the
agency is proposing that the warning telltale must become illuminated
not more than ten minutes after a tire becomes significantly under-
inflated.
4. Duration of Warning
NHTSA believes that the TPMS warning telltale should be illuminated
as long as any of the vehicle's tires remains significantly under-
inflated. The agency believes that a driver is more likely to take
corrective action if the warning provided is continuous. Thus, in both
alternatives, the agency is proposing that the warning telltale remain
illuminated as long as any of the vehicle's tires remains significantly
under-inflated, and the ignition switch is in the ``on'' (``run'')
position, whether or not the engine is running.
The agency would like to receive comments specifically addressing
this proposed requirement. Would both direct and indirect TPMSs be able
to meet this?
5. Self-Check
During vehicle start-up, many vehicle systems provide a system
readiness self-check or a bulb-check to provide an initial indication
to the driver that the system is operational. NHTSA is aware that it is
necessary to drive vehicles with indirect TPMSs for some distance so
that the system can calibrate. As a result, these systems may not be
capable of completing a full system self-check before the vehicle is
driven. The agency also has no data indicating how often bulbs burn
out. As a result, the agency is not proposing a system self-check or a
bulb-check requirement. The agency requests comments on whether the
standard should require a complete system check, a bulb-check, or no
check.
E. System Calibration and Reset
NHTSA notes that most indirect TPMSs need substantial time to
calibrate the system, i.e., to ``learn'' the variables associated with
distinct tire types under varying driving conditions. The VRTC found
that the four indirect TPMSs it evaluated took anywhere from several
minutes to several hours to calibrate. This calibration is necessary
when a vehicle is first driven, when the pressure in a tire is changed,
and when the tires are rotated or replaced.
Indirect TPMSs do not indicate that the system is in calibration
mode. During the calibration mode, the system is not monitoring tire
pressure. Thus, if one or more tires becomes significantly under-
inflated while the system is calibrating, the driver would not be
alerted.
The agency is not proposing in either alternative that the TPMS
indicate to the driver that the system is in calibration mode. The
value of such an indication would likely be negligible since the system
would only rarely be in that mode. Recalibration by the driver would
typically occur only after replacing, rotating or reinflating tires.
Nevertheless, the agency requests comment on this. Should this
requirement be included?
NHTSA also notes that some TPMSs automatically extinguish the
warning telltale when the inflation pressure in a tire rises above the
threshold level for warning indication. These systems thus require no
action on the part of the driver.
Other TPMSs make it necessary for the driver to reset the system by
means of a reset button after taking action to resolve the low tire
pressure problem. This may invite human error or abuse. For example, a
driver may accidentally press the reset button when one or more of the
vehicle's tires is under-inflated, but not under-inflated enough to
illuminate the low tire pressure warning telltale. This would re-
calibrate the system so that the under-inflated condition would be
accepted as a normal variable. The indirect TPMS then would not be able
to detect a significantly under-inflated tire until one or more tires
was 20 percent or more lower than it already was. This could also occur
if the driver simply pressed the reset button when the low tire
pressure warning telltale illuminated. The indirect TPMS would re-
calibrate the system so that the under-inflated condition would be
accepted as a normal variable, and the system would not be able to
detect a significantly under-inflated tire until it was 20 percent or
more lower than it already was.
The agency is proposing that the warning telltale deactivate,
manually or automatically, only when all of the vehicle's tires cease
to be significantly under-inflated. The agency requests comment on this
potential problem.
F. System Failure
NHTSA is not proposing that the TPMS must alert the driver in the
event of a system malfunction, e.g., by adding a separate system
failure telltale. The agency believes that such a requirement might be
too costly. However, NHTSA solicits comments on this issue. How
difficult would it be to add a system malfunction feature to TPMSs?
What are the possible safety benefits of such a feature?
G. Number of Tires Monitored
In the first alternative, the agency is proposing that the TPMS be
able to detect when one to four tires becomes significantly under-
inflated. In the second alternative, the agency is proposing that the
TPMS be able to detect when one to three tires becomes significantly
under-inflated. The reason for this difference is that direct TPMSs can
detect when all four tires become significantly under-inflated, but
most indirect TPMSs cannot.
The agency is requesting comments on whether the second alternative
should require that the TPMS be able to detect when all four tires
become significantly under-inflated. Under both alternatives, indirect
TPMSs would require some improvements in their performance. Current
indirect TPMSs that can detect under-inflation only when a tire is 30
percent or more below would have to be improved so they could meet the
25 percent under-inflation requirement for one to three tires. Would
requiring that indirect TPMSs be able to detect when all four tires
become significantly under-inflated be a reasonable goal? What would
the additional benefits and costs of such a requirement be?
H. Replacement Tires/Rims
NHTSA believes that it is important that a TPMS be able to function
[[Page 38994]]
properly when the vehicle's original tires are replaced. Thus, the
agency is proposing to require that each TPMS be able to meet the
requirements of the new standard when any of the vehicle's original
tires or rims are replaced with any optional or replacement tire/rim
size(s) recommended for use on the vehicle by the vehicle manufacturer.
I. Monitoring of Spare Tire
The Federal motor vehicle safety standards do not require vehicles
to be equipped with a spare tire. Thus, the agency is not proposing
that the TPMS monitor the pressure in the spare tire while it is
stowed.
J. Written Instructions
NHTSA is proposing that the vehicle's owner's manual provide an
image of the TPMS symbol with the following information, in English:
``When the TPMS warning light is lit, one of your tires is
significantly under-inflated. You should stop and check your tires as
soon as possible, and inflate them to the proper pressure as indicated
on the vehicle's tire inflation placard. Driving on an under-inflated
tire causes the tire to overheat and can eventually lead to tire
failure. Under-inflation also reduces fuel efficiency and tire tread
life, and may affect the vehicle's handling and stopping ability.''
Each vehicle manufacturer may, at its discretion, provide additional
information about the significance of the low tire pressure warning
telltale illuminating and description of corrective action to be
undertaken.
The agency believes that drivers would need this information so
that they would know what to do if the low tire pressure warning
telltale illuminates. The agency also believes that more drivers will
inflate their tires, and thus experience the benefits associated with
properly inflated tires, if they understand the potential consequences
of significantly under-inflated tires. The agency requests comments
addressing this issue. Is this information sufficient, or should the
agency require additional information in the owner's manual?
K. Temperature Compensation
During the driving of a motor vehicle, the temperature in its tires
increases. The increased temperature causes increases in the inflation
pressure in the tire.\15\ This phenomenon could impact the ability of a
TPMS to measure or calculate the actual pressure in a tire accurately.
A temperature compensation feature in a TPMS compensates for the
increased inflation due to temperature increases. Some direct TPMSs
employ pressure and temperature sensors located in the wheel. The
agency is aware of no indirect TPMSs that are capable of compensating
for temperature increases in tires.
---------------------------------------------------------------------------
\15\ The actual tire pressure increase due to heat appears to
depend on several factors, including whether the tire is under-
inflated to start with, the load on the tire, and how much braking
has occurred recently. The agency believes that the maximum increase
in tire pressure due to increased temperature is 4 psi.
---------------------------------------------------------------------------
It is possible that, without temperature compensation, the
illumination of the low tire pressure warning telltale could be delayed
due to the increased pressure caused by increased temperature. The
telltale also could be extinguished due to the increased tire pressure
experienced during normal operation. In addition, large fluctuations in
the ambient temperature could result in the low tire pressure warning
telltale's being activated on vehicles during ignition, and then de-
activated after the vehicle has been driven for awhile and the
temperature (and thus the pressure) in a tire increases.
NHTSA is not proposing to require a temperature compensation
feature in either proposed alternative. The agency believes such a
requirement would have limited value and add slightly to the cost of
the proposed standard. The agency also believes that indirect TPMSs
would not be able to meet such a requirement. However, the agency is
concerned that TPMSs without a temperature compensation feature could
allow the cold tire pressure to fall below the absolute minimum
inflation pressure proposed in Table 1 without warning the driver. The
agency requests comments on whether the standard should include a
temperature compensation requirement, and what the safety benefits and
costs of such a requirement would be. Also, if NHTSA did require a
temperature compensation feature, how would the agency test/regulate
it?
Alternatively, the agency could amend the test procedures to
specify a cool-down period for tires after a vehicle's TPMS has been
tested. This may make the tests more repeatable and accurate. The
agency requests comments on this issue.
L. Test Conditions
Under both alternatives, NHTSA is proposing that each vehicle be
tested at its gross vehicle weight rating (GVWR) and its lightly loaded
vehicle weight (LLVW), defined as unloaded vehicle weight plus up to
400 pounds (including test driver and instrumentation). The ambient
temperature would be between 0 deg.C (32 deg.F) and 40 deg.C
(104 deg.F). The test road surface would be dry and smooth. The vehicle
would be tested at a speed between 50 km/h (31.1 mph) and 100 km/h
(62.2 mph).
The agency requests comments on these test conditions. For example,
some indirect TPMSs require the vehicle to be driven at a variety of
speeds, including stops and starts, to calibrate. The agency is
proposing that vehicles be tested at a speed between 50 km/h and 100
km/h. This would exclude the stops and starts necessary for some
indirect TPMSs to calibrate. It also would necessitate the use of
nonpublic test courses, as opposed to public roads, for testing
purposes. At what speeds should vehicles be tested? Are there any other
driving conditions under which vehicles should be tested?
M. Test Procedures
In both alternatives, NHTSA is proposing that the vehicle's tires
be inflated to the vehicle manufacturer's recommended cold inflation
pressure. Then the vehicle would be driven between 50 km/h and 100 km/h
for up to 20 minutes.
Under the first alternative, while driving at that speed, any
combination of tires (from one to all four) is deflated until it is
significantly under-inflated. Then the elapsed time between the time
the vehicle's tire or combination of tires becomes significantly under-
inflated and the time the low tire pressure warning telltale is
illuminated is recorded. After the warning telltale illuminates,
pressure is added to the tire or combination of tires that was deflated
such that the tire or each of those tires is one psi below the level of
significant under-inflation. Then the warning telltale is checked to
see if it remains illuminated. If the warning telltale remains
illuminated, a manual reset is attempted.
Under the second alternative, the procedures are the same, except
any combination of tires (from one to three) is deflated until it is
significantly under-inflated.
Under both alternatives, the agency is proposing that the test
procedures be repeated for each tire and rim combination recommended by
the vehicle manufacture for that vehicle. The agency requests comments
on whether there are any steps that should be taken between testing
different tire and rim combinations and that should be added to the
test procedures.
The agency requests comment on all aspects of these test
procedures. Should
[[Page 38995]]
the agency specify more or less than 20 minutes for the system to
calibrate? As noted above in the section on Temperature Compensation,
the inflation pressure in tires increases as they heat up during normal
operation. This may cause variations in testing. To ensure
repeatability, should the agency specify that tires be tested cold? Are
there any other procedures the agency should specify?
N. Human Factors
There are two human factors issues involved with TPMSs. The first
is what information is displayed to the driver and how that information
is displayed. The second is whether the driver responds to the
information by checking and inflating the vehicle's tires.
Regarding the information displayed to the driver, NHTSA is
proposing only a warning telltale that would illuminate when one or
more of the vehicle's tires becomes significantly under-inflated. The
agency is not proposing that the pressure in each tire be displayed.
However, in NHTSA's analysis of the benefits, both in the PEA and
below, the agency assumes that manufacturers who install direct TPMSs
will display the pressure in each tire because it will be helpful to
drivers in terms of safety, fuel economy, and tread life. Most indirect
TPMSs are not capable of displaying the pressure in each tire.
The agency anticipates that drivers would react differently to the
different information they receive from TPMSs. Some drivers of vehicles
equipped with a direct TPMS would keep track of the pressure in each
tire and add pressure to their tires whenever necessary, even before
the warning telltale becomes illuminated. These drivers would accrue
more benefits in terms of increased safety, fuel efficiency, and tread
life than drivers who wait until the warning telltale becomes
illuminated.
On the other hand, some drivers who currently check and inflate
their own tires frequently enough to avoid significant under-inflation
may start to rely on the TPMS warning telltale to indicate under-
inflation. The agency believes that this would happen more often with
drivers of vehicles equipped with an indirect TPMS, which only
illuminate a warning telltale when one or more tires becomes
significantly under-inflated, than with drivers of vehicles equipped
with a direct TPMS, which display the pressure in each tire. These
drivers would accrue fewer benefits in terms of safety, fuel
efficiency, and tread life.
NHTSA does not have any information on which to base an estimate of
the percentage of drivers who would use the information from a display
of the pressure in each tire to inflate their tires more frequently
than they currently do, or the percentage of drivers who would rely on
the TPMS warning telltale to indicate under-inflation and inflate their
tires less frequently than they currently do. The agency requests
comment on this issue.
VI. Benefits
Following is a summary of the benefits associated with the two
proposed alternatives. For a more detailed analysis, see the agency's
Preliminary Economic Assessment (PEA). A copy of the PEA has been
placed in the docket.
For purposes of this analysis, the agency assumed that vehicles
with a direct TPMS will display a continuous readout of the pressure in
each tire and have a warning telltale that illuminates when the
vehicle's tires become significantly under-inflated. The agency assumed
that 80 percent of drivers would react to this tire-specific
information and re-inflate the significantly under-inflated tire(s).
For indirect TPMSs, the agency assumed that only 60 percent of drivers
would react to a low tire pressure warning telltale and re-inflate
their significantly under-inflated tire(s). The agency requests
comments on these assumptions.
The safety benefits that the agency has quantified come from
calculations of a reduction in stopping distance for vehicles with
properly inflated tires. NHTSA notes that the relationship of tire
inflation to stopping distance is influenced by road conditions (i.e.,
wet versus dry), as well as by the road surface composition.
In tests conducted by Goodyear, significant increases were found in
the stopping distance of tires that were under-inflated. By contrast,
tests conducted by NHTSA at the VRTC testing ground found only minor
differences in stopping distance. In some cases, these distances
actually decreased with lower inflation pressure. The VRTC tests also
found only minor differences between wet and dry road surface stopping
distance.
It is likely that some of these differences are due to test track
surface characteristics. The VRTC track surface is considered to be
extremely aggressive in that it allows for maximum friction with tire
surfaces. It is more representative of a new road surface than the worn
surfaces on the vast majority of roads.
The Goodyear tests may be biased in other ways. Their basic wet
surface tests were conducted on surfaces with .05 inch of standing
water. This more than typically would be encountered under normal wet
road driving conditions, and thus may exaggerate the stopping distances
experienced under most circumstances. On the other hand, crashes are
more likely to occur under more hazardous conditions, which may mean
that the Goodyear data are less biased when applied to the actual
crash-involved population.
Generally speaking, the Goodyear test results imply a significant
impact on stopping distance from properly inflated tires, while the
VRTC test results imply these impacts would be minor or nonexistent.
The analysis below and in the PEA estimates stopping distance impacts
using the Goodyear data to establish an upper range of potential
benefits. A lower range of no benefit is implied by the current VRTC
test results. The estimates detailed below are the mid-points between
the upper and lower range of potential benefits.
The benefits from preventable crashes were assumed to occur over
all crash types and severities. This assumption recognizes that there
are a variety of crash circumstances for which marginal reductions in
stopping distance may prevent the crash from occurring. Crash
prevention may be more likely under some circumstances than others. For
example, it is possible that a larger portion of side impact crashes
than head-on crashes might be prevented. In side impact crashes where
vehicles are moving perpendicular to each other, reduced stopping
distance by one vehicle reduces the speed at which it enters the crash
zone and potentially allows the second vehicle to move through the
crash zone, thus avoiding the impact. In a head-on collision, both
vehicles are moving toward the crash and a reduction in stopping
distance for one vehicle may not improve the chances of avoiding the
crash as much as in a side impact situation. Moreover, if a separate
analysis were conducted for different crash types and severities, the
portion of crashes prevented would be greater for crashes at higher
speeds. However, NHTSA does not have sufficient information to conduct
a separate analysis of each crash circumstance. Instead, the agency has
used an overall estimate across all crash types. The agency requests
comment on this issue.
A. First Alternative
The first alternative would require the TPMS to illuminate the low
tire pressure warning telltale when pressure in any tire or combination
of tires decreases to 20 percent below the vehicle manufacturer's
recommended
[[Page 38996]]
cold inflation pressure for the vehicle's tires or the absolute value
specified in proposed Table 1, whichever is higher. Thus, the TPMS
would have to provide warning when any number of tires, from one to
four tires, is significantly under-inflated.
When a vehicle's tires are under-inflated, and it is traveling on a
wet surface, the vehicle takes longer to stop than when its tires are
properly inflated. For example, according to data from Goodyear, a
vehicle traveling at 62 mph on a wet surface takes about 442 feet to
stop if its tires are properly inflated. If its tires are under-
inflated by 20 percent, the vehicle takes about 462 feet to stop.
The Goodyear data indicates that, under the first alternative, the
average stopping distance of passenger cars across all speeds and
driving conditions would be reduced from 137 feet (the average stopping
distance for a vehicle with tires 20 percent under-inflated) to 132.1
feet (the average stopping distance for a vehicle with properly
inflated tires). The average stopping distance of light trucks would be
reduced from 131.5 feet to 127.3 feet. This would reduce the number of
crashes involving braking passenger cars by 3.6 percent and braking
light trucks by 3.2 percent. The other 96.4 percent of crashes
involving braking passenger cars and 96.8 percent of crashes involving
braking light trucks would still occur, but at a reduced impact speed.
The agency estimates that this would result in 79 fewer fatalities and
would prevent or reduce in severity 10,635 nonfatal injuries.\16\
---------------------------------------------------------------------------
\16\ The range of injuries prevented would be 0 to 21,270, and
the range of deaths prevented would be 0 to 158.
---------------------------------------------------------------------------
Correct tire pressure also improves a vehicle's fuel economy.
Recent data from Goodyear indicate that a vehicle's fuel efficiency is
reduced by one percent for every 2.96 psi that its tires are below the
vehicle manufacturer's recommended cold inflation pressure. NHTSA
estimates that, under the first alternative, the average vehicle would
get a little over 2 percent higher fuel economy. This translates into
an average discounted value of $32.22 (in 2001 dollars) over the
lifetime of the vehicle for passenger cars and light trucks.
Correct tire pressure also increases a tire's life. Data from
Goodyear indicate that for every 1 psi drop in tire pressure, tread
life decreases by 1.78 percent. NHTSA estimates that under the first
alternative, the average tire life would increase by 1,404 miles for
passenger cars and 1,972 miles for light trucks. This would delay new
tire purchases. The agency estimates that the average discounted value
of these delayed tire purchases is $5.26 for passenger cars and $16.80
for light trucks.
B. Second Alternative
The second alternative requires the TPMS to illuminate the low tire
pressure warning telltale when pressure in any tire or combination of
tires, up to a total of three tires, decreases to 25 percent below the
vehicle manufacturer's recommended cold inflation pressure for the
vehicle's tires, or the absolute value specified in proposed Table 1,
whichever is higher.
NHTSA estimates that the second alternative would also reduce a
vehicle's stopping distance. However, since the pressure level at which
the driver is warned is lower in the second alternative (25 percent
versus 20 percent), fewer drivers would receive a low tire pressure
warning. Thus, fewer drivers would inflate their tires to the proper
pressure, and fewer vehicles would experience the reduced stopping
distance. Consequently, the agency estimates that under the second
alternative, the reduction in stopping distance would result in 49
fewer fatalities and would prevent or reduce in severity 6,585 nonfatal
injuries.\17\
---------------------------------------------------------------------------
\17\ The range of injuries prevented would be 0 to 13,170, and
the range of deaths prevented would be 0 to 97.
---------------------------------------------------------------------------
NHTSA estimates that under the second alternative, vehicles' fuel
economy would be improved. However, fewer vehicles would experience
this improvement for the reasons stated in the previous paragraph.
Consequently, the agency estimates that under the second alternative,
improved fuel economy would translate into an average discounted value
of $16.40 (in 2001 dollars) over the lifetime of the vehicle for
passenger cars and light trucks.
NHTSA estimates that under the second alternative, tire life would
be increased by 1,131 miles for passenger cars and 1,615 miles for
light trucks if they are equipped with a direct TPMS. If they are
equipped with an indirect TPMS, the agency estimates that tire life
would be increased by 635 miles for passenger cars and 615 miles for
light trucks. This would delay new tire purchases. The agency estimates
that the average discounted value of these delayed tire purchases is
$4.24 for passenger cars and $13.84 for light trucks if they are
equipped with a direct TPMS, and $2.39 for passenger cars and $5.17 for
light trucks if they are equipped with an indirect TPMS.
NHTSA notes that longer tire life is an economic benefit rather
than a safety benefit. The agency is concerned that tires' tread may
last longer than other parts of the tire, e.g., the sidewall. Most
drivers change their tires when the tread is low. If the tread outlasts
the rest of the tire, the tire may fail. The agency believes that part
of the cause of the Firestone problem was that the tread lasted longer
than expected, allowing other failures to occur. The agency requests
comment on this issue.
C. Unquantified Benefits
The agency believes the proposals would also result in other
benefits, such as fewer crashes resulting from tire blowouts, adverse
effects on vehicle handling due to inflation pressure loss and
hydroplaning, from fewer crashes involving vehicles that had been
stopped by the side of the road because of a flat tire, and the
prevention of the property damage that results from these crashes. For
more information on these unquantified benefits, see the PEA. NHTSA has
not attempted to quantify those benefits. The agency requests comment
on these unquantified benefits.
VII. Costs
A. Indirect TPMSs
The costs of incorporating an indirect TPMS into a vehicle would
vary depending on the way in which the incorporation is accomplished.
In order to add a current ABS-based indirect TPMS to a motor vehicle
that already has an ABS, the agency assumes that the vehicle's
manufacturer would only have to add the capability to monitor the wheel
speed sensors, a low tire pressure warning telltale, and a reset
button, and make some software changes. NHTSA estimates that the cost
of adding these features would be about $12.90 per vehicle. However, as
explained below, the agency is uncertain whether the resulting ABS-
based indirect TPMS would comply with either alternative.
NHTSA tested four current ABS-based indirect TPMSs. None of the
four met the proposed requirements for either alternative. These TPMSs
had problems detecting two significantly under-inflated tires on the
same axle and on the same side of the vehicle. They also did not
illuminate the low tire pressure warning telltale when the pressure in
the vehicle's tires decreased to 20 percent, or even 25 percent, below
the vehicle manufacturer's recommended cold inflation pressure. NHTSA
does not know whether improving current indirect TPMSs to meet the
requirements of either alternative would
[[Page 38997]]
result in additional costs. The agency requests comments on this issue.
Pickup trucks comprise about 40 percent of light truck sales. Some
percentage of pickup trucks that have ABS have only one wheel speed
sensor for the rear axle. In order to meet the requirements of either
proposed alternative, NHTSA believes vehicle manufacturers would have
to add a fourth wheel speed sensor to these trucks at an estimated cost
of $20 per vehicle. The agency assumes for this analysis that about 10
percent of all light trucks, or 7.5 percent of all light vehicles with
ABS, would be in this category. However, the agency requests comment on
the percentage of pickup trucks that would require this modification.
For vehicles currently without ABS, there are two indirect
measurement choices. First, the vehicle manufacturer could add ABS and
the necessary TPMS features to the vehicle. NHTSA estimates that this
would cost about $240 per vehicle. The agency does not expect
manufacturers that make this choice unless they are already planning
for other reasons to add ABS. Second, the vehicle manufacturer could
add wheel speed sensors and the necessary TPMS features to the vehicle.
NHTSA estimates that this approach would cost about $130 per vehicle.
B. Direct TPMSs
There are two main costs associated with direct TPMSs: sensors and
a receiver. There is a wide disparity in costs for sensors, depending
on what type of information is sensed. Providing pressure sensors would
cost from $5 to $10 per wheel, or $20 to $40 per vehicle.
The cost of the receiver depends upon whether the vehicle already
has a receiver capable of receiving and processing the information
coming from the sensors. NHTSA estimates that about 60 percent of
vehicles currently have such a receiver. Making some software changes
and adding a display showing the pressure for each tire would cost
about $25 per vehicle. The 40 percent of vehicles without such a
receiver would have to be equipped with a receiver, a display, and the
necessary software. The agency estimates that this would cost about $40
to $50 per vehicle.
The agency estimates that installation costs for a direct TPMS
would be about $4 per vehicle.
Thus, the agency estimates that the cost of adding a direct TPMS to
a vehicle that is already equipped with a receiver would be $49 to $69.
For a vehicle that is not already equipped with a receiver, the cost
would be $64 to $94. The agency used the midpoints of $59 and $79 to
determine the cost per vehicle of the first alternative
NHTSA determined the current use of TPMSs in new vehicles by using
the calendar year 2000 sales, a model year 2001 list of the makes and
models with each type of system, and an estimate that 2 percent of
sales were purchased as an option on those models that offered a TPMS
as an option. As a result, the agency estimates that 4 percent of the
model year 2001 light vehicle fleet has an indirect TPMS, and 1 percent
of the fleet has a direct TPMS.
NHTSA conducted tear down studies of two currently available direct
TPMSs, one produced by Beru and the other produced by Johnson Controls.
The agency chose the Beru TPMS because it is considered top-of-the-
line. It also was the most expensive direct TPMS the agency found on
the market, at a cost of $200. The Johnson Controls direct TPMS, on the
other hand, is typical of most direct TPMSs. It cost only $69, similar
to the costs estimated by the agency.
C. Testing and Maintenance Costs
There are some costs that would be associated with both direct and
indirect TPMSs. For example, both systems would have to be tested for
compliance with the proposed requirements. The agency estimates that
the man-hours required to complete the testing would be 6 hours for a
manager, 30 hours for a test engineer, and 30 hours for a test
technician/driver. The agency estimates labor costs would be $75 per
hour for a manager, $53 per hour for a test engineer, and $31 per hour
for a test technician/driver. Thus, the agency estimates total testing
costs would be $2,970 per vehicle model.
D. Unquantified Costs
The agency believes the proposals may also result in additional
costs, such as the cost of replacing worn or damaged TPMS equipment,
the cost of replacing batteries in a direct TPMS, and the cost of the
time it would take for a driver to react to a low tire pressure warning
by pulling over to a gas station to check and inflate the vehicle's
tires. NHTSA has not attempted to quantify those costs. The agency
requests comment on these unquantified costs.
E. First Alternative
Assuming that installation of a direct TPMS would be necessary to
achieve compliance, the agency estimates that the average incremental
cost would be $66.33 per vehicle. This would result in an average net
cost of $23.08 per vehicle ($66.33-$32.22 (fuel savings)-$11.03 (tread
wear savings)), and a net cost per equivalent life saved of $1.9
million. The total annual cost would be about $1.06 billion, or $369
million when the fuel and tread wear savings are factored in.
F. Second Alternative
An indirect TPMS for all passenger cars and light trucks that are
already equipped with an ABS would cost an average of $12.90 per ABS-
equipped vehicle. The agency assumes that vehicle manufacturers would
choose to equip vehicles that are not equipped with an ABS with a
direct TPMS because it is cheaper than adding wheel speed sensors or an
ABS. The average cost of adding a direct TPMS would be $66.33 per
vehicle. The agency estimates that the overall cost of the second
alternative would be $30.54 per vehicle, since 67 percent of vehicles
are equipped with an ABS, while 33 percent are not. This would result
in an average net cost of $8.63 ($30.54-$16.40 (fuel savings)-$5.51
(tread wear savings)) per vehicle, and a net cost per equivalent life
saved of $1.1 million. The total annual cost would be about $489
million, or $138 million when the fuel and tread wear savings are
factored in.
VIII. Lead-Time
The TREAD Act requires that this rule take effect two years after
the final rule is issued. Since the final rule must be issued by
November 1, 2001, the rule must take effect not later than November 1,
2003.
NHTSA requests comment on whether vehicle manufacturers will be
able to meet the statutory deadline, and whether TPMS manufacturers
will be able to supply enough TPMSs to meet the demand under either of
the alternatives proposed in this NPRM.
The agency requests comments also on whether a phase-in beginning
on November 1, 2003, would be appropriate. Such a phase-in might
provide for the compliance of 35 percent of production in the first
year (2003), 65 percent in the second year (2004), and 100 percent in
the third year (2005). If a phase-in were adopted, should carry forward
credit be given for early compliance?
IX. Rulemaking Analyses and Notices
A. Executive Order 12866 and DOT Regulatory Policies and Procedures
Executive Order 12866, ``Regulatory Planning and Review'' (58 FR
51735, October 4, 1993), provides for making
[[Page 38998]]
determinations whether a regulatory action is ``significant'' and
therefore subject to Office of Management and Budget (OMB) review and
to the requirements of the Executive Order. The Order defines a
``significant regulatory action'' as one that is likely to result in a
rule that may:
(1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or Tribal governments or
communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations of recipients
thereof; or
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
This proposal is economically significant. Accordingly, it was
reviewed under Executive Order 12866. The rule is also significant
within the meaning of the Department of Transportation's Regulatory
Policies and Procedures. The agency has estimated that compliance with
this proposed rule would cost from $30.54 to $66.33 per vehicle per
year. Since approximately 16 million vehicles are produced for the
United States market each year, this proposal would have greater than a
$100 million effect.
Because this proposed rule is significant, the agency has prepared
a Preliminary Economic Analysis (PEA). This analysis is summarized
above in the sections on Benefits and Costs. The PEA is available in
the docket and has been placed on the agency's website along with the
proposal itself.
B. Regulatory Flexibility Act
Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq.,
as amended by the Small Business Regulatory Enforcement Fairness Act
(SBREFA) of 1996), whenever an agency is required to publish a notice
of rulemaking for any proposed or final rule, it must prepare and make
available for public comment a regulatory flexibility analysis that
describes the effect of the rule on small entities (i.e., small
businesses, small organizations, and small governmental jurisdictions).
The Small Business Administration's regulations at 13 CFR part 121
define a small business, in part, as a business entity ``which operates
primarily within the United States.'' (13 CFR 121.105(a)). No
regulatory flexibility analysis is required if the head of an agency
certifies the rule will not have a significant economic impact on a
substantial number of small entities. SBREFA amended the Regulatory
Flexibility Act to require Federal agencies to provide a statement of
the factual basis for certifying that a rule will not have a
significant economic impact on a substantial number of small entities.
NHTSA has considered the effects of this proposed rule under the
Regulatory Flexibility Act. I certify that this proposed rule would not
have a significant economic impact on a substantial number of small
entities. The rationale for this certification is that currently there
are only four small motor vehicle manufacturers in the United States
that would have to comply with this proposed rule. These manufacturers
would have to rely on suppliers to provide the TPMS hardware, and then
they would have to integrate the TPMS into their vehicles.
There are a few small manufacturers that manufacture recreational
vehicles which would have to comply with this proposed rule. However,
most of these manufacturers use van chassis supplied by the larger
manufacturers, e.g., General Motors, Ford, or DaimlerChrysler, and
could use the TPMSs supplied with the chassis. These manufacturers also
would not have to test the TPMS for compliance with this proposed rule
since they would be able to rely upon the chassis manufacturer's
incomplete vehicle documentation.
C. National Environmental Policy Act
NHTSA has analyzed this rulemaking action for the purposes of the
National Environmental Policy Act. The agency has determined that
implementation of this proposed rule would not have any significant
impact on the quality of the human environment.
D. Executive Order 13132 (Federalism)
Executive Order 13132 requires NHTSA to develop an accountable
process to ensure ``meaningful and timely input by State and local
officials in the development of regulatory policies that have
federalism implications.'' ``Policies that have federalism
implications'' is defined in the Executive Order to include regulations
that have ``substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government.'' Under Executive Order 13132, the agency may not issue a
regulation with Federalism implications, that imposes substantial
direct compliance costs, and that is not required by statute, unless
the Federal government provides the funds necessary to pay the direct
compliance costs incurred by State and local governments, the agency
consults with State and local governments, or the agency consults with
State and local officials early in the process of developing the
proposed regulation. NHTSA also may not issue a regulation with
Federalism implications and that preempts State law unless the agency
consults with State and local officials early in the process of
developing the proposed regulation.
The agency has analyzed this proposed rule in accordance with the
principles and criteria set forth in Executive Order 13132 and has
determined that it would not have sufficient federalism implications to
warrant consultation with State and local officials or the preparation
of a federalism summary impact statement. The proposal would not have
any substantial effects on the States, or on the current Federal-State
relationship, or on the current distribution of power and
responsibilities among the various local officials.
E. Civil Justice Reform
This proposed amendment would not have any retroactive effect.
Under 49 U.S.C. 30103, whenever a Federal motor vehicle safety standard
is in effect, a State may not adopt or maintain a safety standard
applicable to the same aspect of performance which is not identical to
the Federal standard, except to the extent that the state requirement
imposes a higher level of performance and applies only to vehicles
procured for the State's use. 49 U.S.C. 30161 sets forth a procedure
for judicial review of final rules establishing, amending, or revoking
Federal motor vehicle safety standards. That section does not require
submission of a petition for reconsideration or other administrative
proceedings before parties may file suit in court.
F. Paperwork Reduction Act
Under the Paperwork Reduction Act of 1995, a person is not required
to respond to a collection of information by a Federal agency unless
the collection displays a valid OMB control number. This proposed rule
would not require any collections of information as defined by the OMB
in 5 CFR Part 1320.
G. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
[[Page 38999]]
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272)
directs us to use voluntary consensus standards in our regulatory
activities unless doing so would be inconsistent with applicable law or
otherwise impractical. Voluntary consensus standards are technical
standards (e.g., materials specifications, test methods, sampling
procedures, and business practices) that are developed or adopted by
voluntary consensus standards bodies, such as the Society of Automotive
Engineers (SAE). The NTTAA directs us to provide Congress, through OMB,
explanations when we decide not to use available and applicable
voluntary consensus standards.
There are no voluntary consensus standards available at this time.
However, NHTSA will consider any such standards when they become
available.
H. Unfunded Mandates Reform Act
Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA)
requires Federal agencies to prepare a written assessment of the costs,
benefits, and other effects of proposed or final rules that include a
Federal mandate likely to result in the expenditure by State, local or
tribal governments, in the aggregate, or by the private sector, of more
than $100 million in any one year (adjusted for inflation with base
year of 1995). Before promulgating a rule for which a written statement
is needed, section 205 of the UMRA generally requires NHTSA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost-effective, or least burdensome alternative
that achieves the objectives of the rule. The provisions of section 205
do not apply when they are inconsistent with applicable law. Moreover,
section 205 allows NHTSA to adopt an alternative other than the least
costly, most cost-effective, or least burdensome alternative if the
agency publishes with the final rule an explanation why that
alternative was not adopted.
This proposed rule would not result in the expenditure by State,
local, or tribal governments, in the aggregate, of more than $100
million annually, but it would result in the expenditure of that
magnitude by vehicle manufacturers and/or their suppliers. This
document seeks comments on two alternatives for achieving the purposes
of the TREAD Act mandate.
I. Plain Language
Executive Order 12866 requires each agency to write all rules in
plain language. Application of the principles of plain language
includes consideration of the following questions:
--Have we organized the material to suit the public's needs?
--Are the requirements in the rule clearly stated?
--Does the rule contain technical language or jargon that is not clear?
--Would a different format (grouping and order of sections, use of
headings, paragraphing) make the rule easier to understand?
--Would more (but shorter) sections be better?
--Could we improve clarity by adding tables, lists, or diagrams?
--What else could we do to make this rulemaking easier to understand?
If you have any responses to these questions, please include them
in your comments on this NPRM.
J. Regulation Identifier Number (RIN)
The Department of Transportation assigns a regulation identifier
number (RIN) to each regulatory action listed in the Unified Agenda of
Federal Regulations. The Regulatory Information Service Center
publishes the Unified Agenda in April and October of each year. You may
use the RIN contained in the heading at the beginning of this document
to find this action in the Unified Agenda.
Comments
How Do I Prepare and Submit Comments?
Your comments must be written and in English. To ensure that your
comments are correctly filed in the Docket, please include the docket
number of this document in your comments.
Your comments must not be more than 15 pages long. (49 CFR 553.21).
We established this limit to encourage you to write your primary
comments in a concise fashion. However, you may attach necessary
additional documents to your comments. There is no limit on the length
of the attachments.
Please submit two copies of your comments, including the
attachments, to Docket Management at the address given above under
ADDRESSES.
In addition, given the statutory deadline of November 1, 2001, for
issuance of the final rule, for those comments of 4 or more pages in
length, we request that you send 10 additional copies, as well as one
copy on computer disc, to: Mr. George Soodoo, Office of Crash Avoidance
Standards, National Highway Traffic Safety Administration, 400 Seventh
Street, SW., Washington, DC 20590. We emphasize that this is not a
requirement. However, we ask that you do this to aid us in expediting
our review of all comments. The copy on computer disc may be in any
format, although we would prefer that it be in WordPerfect 8 or Word
2000.
You may also submit your comments to the docket electronically by
logging onto the Dockets Management System website at http://dms.dot.gov. Click on ``Help & Information'' or ``Help/Info'' to obtain
instructions for filing the document electronically.
How Can I Be Sure That My Comments Were Received?
If you wish Docket Management to notify you upon its receipt of
your comments, enclose a self-addressed, stamped postcard in the
envelope containing your comments. Upon receiving your comments, Docket
Management will return the postcard by mail.
How Do I Submit Confidential Business Information?
If you wish to submit any information under a claim of
confidentiality, you should submit three copies of your complete
submission, including the information you claim to be confidential
business information, to the Chief Counsel, NHTSA, at the address given
above under FOR FURTHER INFORMATION CONTACT. In addition, you should
submit two copies, from which you have deleted the claimed confidential
business information, to Docket Management at the address given above
under ADDRESSES. When you send a comment containing information claimed
to be confidential business information, you should include a cover
letter setting forth the information specified in our confidential
business information regulation. (49 CFR part 512.)
Will the Agency Consider Late Comments?
We will consider all comments that Docket Management receives
before the close of business on the comment closing date indicated
above under DATES. To the extent possible, we will also consider
comments that Docket Management receives after that date. If Docket
Management receives a comment too late for us to consider it in
developing a final rule (assuming that one is issued), we will consider
that comment as an informal suggestion for future rulemaking action.
How Can I Read the Comments Submitted by Other People?
You may read the comments received by Docket Management at the
address
[[Page 39000]]
given above under ADDRESSES. The hours of the Docket are indicated
above in the same location.
You may also see the comments on the Internet. To read the comments
on the Internet, take the following steps:
1. Go to the Docket Management System (DMS) Web page of the
Department of Transportation (http://dms.dot.gov/).
2. On that page, click on ``search.''
3. On the next page (http://dms.dot.gov/search/), type in the four-
digit docket number shown at the beginning of this document. Example:
If the docket number were ``NHTSA-1998-1234,'' you would type ``1234.''
After typing the docket number, click on ``search.''
4. On the next page, which contains docket summary information for
the docket you selected, click on the desired comments. You may
download the comments. Although the comments are imaged documents,
instead of word processing documents, the ``pdf'' versions of the
documents are word searchable.
Please note that even after the comment closing date, we will
continue to file relevant information in the Docket as it becomes
available. Further, some people may submit late comments. Accordingly,
we recommend that you periodically check the Docket for new material.
List of Subjects in 49 CFR Part 571
Imports, Motor vehicle safety, Reporting and recordkeeping
requirements, Tires.
In consideration of the foregoing, NHTSA proposes to amend 49 CFR
part 571 as follows:
PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS
1. The authority citation for part 571 would continue to read as
follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;
delegation of authority at 49 CFR 1.50.
2. In section 571.101, in Table 2, two new entries would be added
at the end of the table to read as follows:
Sec. 571.101 Standard No. 101; controls and displays.
* * * * *
Table 2.--Identification and Illustration of Displays
----------------------------------------------------------------------------------------------------------------
Column 1 Column 2 Column 3 Column 4 Column 5
----------------------------------------------------------------------------------------------------------------
Display......................... Telltale Color.... Identifying Words Identifying Symbol Illumination.
or Abbreviation.
----------------------------------------------------------------------------------------------------------------
* * * * *
BILLING CODE 4910-59-P
[[Page 39001]]
[GRAPHIC] [TIFF OMITTED] TP26JY01.001
[[Page 39002]]
[GRAPHIC] [TIFF OMITTED] TP26JY01.002
BILLING CODE 4910-59-C
3. Section 571.138 would be added to read as follows:
Sec. 571.138 Standard No. 138; tire pressure monitoring systems.
[FIRST ALTERNATIVE FOR S1 THROUGH S6]
S1. Purpose and scope. This standard specifies performance
requirements for tire pressure monitoring systems to prevent
significant under-inflation of tires and the resulting safety problems.
S2. Application. This standard applies to passenger cars,
multipurpose passenger vehicles, trucks, and buses that have a gross
vehicle weight rating of 4,536 kilograms (10,000 pounds) or less, and
that are manufactured on or after [The date that is two years after
date of publication of final rule.].
S3. Definitions. The following definitions apply to this standard:
Lightly loaded vehicle weight means unloaded vehicle weight, plus
up to 400 pounds (including test driver and instrumentation).
Significantly under-inflated means any inflation pressure that is
equal to or less than either the pressure 20 percent below the vehicle
manufacturer's recommended cold inflation pressure, or the pressure
specified in the 3rd column of Table 1 of this standard for the
corresponding type of tire, whichever is higher.
Tire pressure monitoring system means a system that detects when
one or more of a vehicle's tires is significantly under-inflated and
illuminates the low tire pressure warning telltale.
S4. Requirements.
S4.1 General. Each vehicle must be equipped with a tire pressure
monitoring system that meets the requirements of S4.2 and S4.3 of this
standard under the test conditions of S5 and the test procedures of S6.
S4.2 Low tire pressure warning telltale.
S4.2.1 Each tire pressure monitoring system must include a low
tire pressure warning telltale that:
(a) Is mounted inside the occupant compartment in clear view of the
driver;
(b) Is identified by the symbol or words shown for the ``Low Tire
Pressure Telltale'' in Table 2 of Standard No. 101 (Sec. 571.101);
(c) Becomes illuminated not more than 10 minutes after any of the
vehicle's tires becomes significantly under-inflated;
(d) Remains illuminated as long as any of the vehicle's tires
remains significantly under-inflated, and the ignition switch is in the
``on'' (``run'') position, whether or not the engine is running; and
(e) Can be deactivated, manually or automatically, only when all of
the vehicle's tires cease to be significantly under-inflated.
S4.2.2 In the case of a telltale that identifies which tires are
significantly under-inflated, each tire in the symbol
[[Page 39003]]
for that telltale must illuminate when the tire it represents is
significantly under-inflated.
S4.3 Replacement tires/rims. Each tire pressure monitoring system
must continue to meet the requirements of this standard when the
vehicle's original tires or rims are replaced with any optional or
replacement tire/rim size(s) recommended for the vehicle by the vehicle
manufacturer.
S4.4 Written instructions. The owner's manual in each vehicle must
provide an image of the TPMS symbol with the following information, in
English: ``When the TPMS warning light is lit, one of your tires is
significantly under-inflated. You should stop and check your tires as
soon as possible, and inflate them to the proper pressure as indicated
on the vehicle's tire inflation placard. Driving on an under-inflated
tire causes the tire to overheat and can eventually lead to tire
failure. Under-inflation also reduces fuel efficiency and tire tread
life, and may affect the vehicle's handling and stopping ability.''
Each vehicle manufacturer may, at its discretion, provide additional
information about the significance of the low tire pressure warning
telltale illuminating and description of corrective action to be
undertaken.
S5. Test conditions.
S5.1 Ambient temperature. The ambient temperature is between
0 deg.C (32 deg.F) and 40 deg.C (104 deg.F).
S5.2 Road test surface. Road tests are conducted on a dry, smooth
roadway.
S5.3 Vehicle conditions.
S5.3.1 Test weight. The vehicle is tested at its lightly loaded
vehicle weight and at its gross vehicle weight rating without exceeding
any of its gross axle weight ratings.
S5.3.2 Vehicle speed. The vehicle is tested at a speed between 50
km/h (31.1 mph) and 100 km/h (62.2 mph).
S6. Test procedures.
(a) Inflate the vehicle's tires to the vehicle manufacturer's
recommended cold inflation pressure.
(b) Drive the vehicle between 50 km/h and 100 km/h for up to 20
minute.
(c) While driving within the speed range specified in paragraph
S6(b) of this standard, deflate any tire or combination of the
vehicle's tires until that tire or each of those tires is significantly
under-inflated.
(d) Continue to drive within the speed range specified in paragraph
S6(b) of this standard. Record the elapsed time between the time when
the vehicle's tire or combination of tires becomes significantly under-
inflated to the time the low tire pressure warning telltale is
illuminated.
(e) After the warning telltale illuminates, add pressure (if
necessary) to the tire or combination of tires that was deflated such
that that tire or each of those tires is one psi below the level of
significant under-inflation. Check to see if the warning telltale
remains illuminated. If the warning telltale remains on, attempt to
manually reset the system in accordance with the written instructions
provided by the vehicle manufacturer.
(f) Repeat the test procedures in paragraphs 6(a) through (e) for
each tire and rim combination recommended for the vehicle by the
vehicle manufacturer.
Tables to Sec. 571.138
Table 1.--Low Tire Pressure Warning Telltale--Minimum Activation Pressure
----------------------------------------------------------------------------------------------------------------
Maximum inflation minimum Pressure activation
------------------------------------------------ pressure
Tire type -------------------------
(kPa) (psi) (kPa) (psi)
----------------------------------------------------------------------------------------------------------------
P-metric--Standard Load............... 240,.................. 35,................... 140 20
300, or............... 44, or................ 140 20
350................... 51.................... 140 20
----------------------------------------------------------------------------------------------------------------
P-metric--Extra Load.................. 280 or................ 41 or................. 160 23
340................... 49.................... 160 23
----------------------------------------------------------------------------------------------------------------
Load Range C.......................... 350................... 51.................... 200 29
----------------------------------------------------------------------------------------------------------------
Load Range D.......................... 450................... 65.................... 260 38
----------------------------------------------------------------------------------------------------------------
Load Range E.......................... 600................... 87.................... 350 51
----------------------------------------------------------------------------------------------------------------
[SECOND ALTERNATIVE FOR S1 THROUGH S6]
S1. Purpose and scope. This standard specifies performance
requirements for tire pressure monitoring systems to prevent
significant under-inflation of tires and the resulting safety problems.
S2. Application. This standard applies to passenger cars,
multipurpose passenger vehicles, trucks, and buses that have a gross
vehicle weight rating of 4,536 kilograms (10,000 pounds) or less, and
that are manufactured on or after [The date that is two years after
date of publication of final rule.].
S3. Definitions. The following definitions apply to this standard:
Lightly loaded vehicle weight means unloaded vehicle weight plus up
to 400 pounds (including test driver and instrumentation).
Significantly under-inflated means any inflation pressure that is
equal to or less than either the pressure 25 percent below the vehicle
manufacturer's recommended cold inflation pressure, or the pressure
specified in the 3rd column of Table 1 of this standard for the
corresponding type of tire, whichever is higher.
Tire pressure monitoring system means a system that detects when
one or more of a vehicle's tires is significantly under-inflated and
illuminates the low tire pressure warning telltale.
S4. Requirements.
S4.1 General. Each vehicle must be equipped with a tire pressure
monitoring system that meets the requirements of S4.2 and S4.3 of this
standard under the test conditions of S5 and the test procedures of S6.
S4.2 Low tire pressure warning telltale.
S4.2.1 Each tire pressure monitoring system must include a low
tire pressure warning telltale that:
(a) Is mounted inside the occupant compartment in clear view of the
driver;
(b) Is identified by the symbol or words shown for the ``Low Tire
Pressure Telltale'' in Table 2 of Standard No. 101 (Sec. 571.101);
(c) Becomes illuminated not more than 10 minutes after any of the
[[Page 39004]]
vehicle's tires becomes significantly under-inflated;
(d) Remains illuminated as long as any of the vehicle's tires
remains significantly under-inflated, and the ignition switch is in the
``on'' (``run'') position, whether or not the engine is running; and
(e) Can be deactivated, manually or automatically, only when all of
the vehicle's tires cease to be significantly under-inflated.
S4.2.2 In the case of a telltale that identifies which tires are
significantly under-inflated, each tire in the symbol for that telltale
must illuminate when the tire it represents is significantly under-
inflated.
S4.3 Replacement tires/rims. Each tire pressure monitoring system
must continue to meet the requirements of this standard when the
vehicle's original tires or rims are replaced with any optional or
replacement tire/rim size(s) recommended for the vehicle by the vehicle
manufacturer.
S4.4 Written instructions. The owner's manual in each vehicle must
provide an image of the TPMS symbol with the following information, in
English: ``When the TPMS warning light is lit, one of your tires is
significantly under-inflated. You should stop and check your tires as
soon as possible, and inflate them to the proper pressure as indicated
on the vehicle's tire inflation placard. Driving on an under-inflated
tire causes the tire to overheat and can eventually lead to tire
failure. Under-inflation also reduces fuel efficiency and tire tread
life, and may affect the vehicle's handling and stopping ability.''
Each vehicle manufacturer may, at its discretion, provide additional
information about the significance of the low tire pressure warning
telltale illuminating and description of corrective action to be
undertaken.
S5. Test conditions.
S5.1 Ambient temperature. The ambient temperature is between
0 deg.C (32 deg.F) and 40 deg.C (104 deg.F).
S5.2 Road test surface. Road tests are conducted on a dry, smooth
roadway.
S5.3 Vehicle conditions.
S5.3.1 Test weight. The vehicle is tested at its lightly loaded
vehicle weight and at its gross vehicle weight rating without exceeding
any of its gross axle weight ratings.
S5.3.2 Vehicle speed. The vehicle is tested at a speed between 50
km/h (31.1 mph) and 100 km/h (62.2 mph).
S6. Test procedures.
(a) Inflate the vehicle's tires to the vehicle manufacturer's
recommended cold inflation pressure.
(b) Drive the vehicle between 50 km/h and 100 km/h for up to 20
minutes.
(c) While driving within the speed range specified in paragraph
S6(b) of this standard, deflate any tire or combination of the
vehicle's tires, up to a total of three tires, until that tire or each
of those tires is significantly under-inflated.
(d) Continue to drive within the speed range specified in paragraph
S6(b) of this standard. Record the elapsed time between the time when
the vehicle's tire or combination of tires becomes significantly under-
inflated to the time the low tire pressure warning telltale is
illuminated.
(e) After the warning telltale illuminates, add pressure (if
necessary) to the tire or combination of tires that was deflated such
that that tire or each of those tires is one psi below the level of
significant under-inflation. Check to see if the warning telltale
remains illuminated. If the warning telltale remains on, attempt to
manually reset the system in accordance with the written instructions
provided by the vehicle manufacturer.
(f) Repeat the test procedures in paragraphs 6(a) through (e) for
each tire and rim combination recommended for the vehicle by the
vehicle manufacturer.
Tables to Sec. 571.138
Table 1.--Low Tire Pressure Warning Telltale--Minimum Activation Pressure
----------------------------------------------------------------------------------------------------------------
Maximum inflation pressure Minimum activation
------------------------------------------------ pressure
Tire type -------------------------
(kPa) (psi) (kPa) (psi)
----------------------------------------------------------------------------------------------------------------
P-metric--Standard Load............... 240,.................. 35,................... 140 20
300, or............... 44, or................ 140 20
350................... 51.................... 140 20
----------------------------------------------------------------------------------------------------------------
P-metric--Extra Load.................. 280 or................ 41 or................. 160 23
340................... 49.................... 160 23
----------------------------------------------------------------------------------------------------------------
Load Range C.......................... 350................... 51.................... 200 29
----------------------------------------------------------------------------------------------------------------
Load Range D.......................... 450................... 65.................... 260 38
----------------------------------------------------------------------------------------------------------------
Load Range E.......................... 600................... 87.................... 350 51
----------------------------------------------------------------------------------------------------------------
Issued: July 23, 2001.
Stephen R. Kratzke,
Associate Administrator for Safety Performance Standards.
[FR Doc. 01-18637 Filed 7-23-01; 1:51 pm]
BILLING CODE 4910-59-P