ITRA responds to NHTSA proposals on tire pressure monitoring systems

Order Reprints

The International Tire & Rubber Association (ITRA) has responded to the National Highway Traffic Safety Administration's (NHTSA) notice of proposed rulemaking on Tire Pressure Monitoring Systems (TPMSs).

In a letter dated Sept. 6, ITRA wrote:

"ITRA's major focus is providing technical assistance and training to the tire, transportation and rubber recycling industries. The educational programs are designed to improve tire performance and reduce lifecycle costs. A major emphasis of ITRA training programs is improving safety for tire users as well as the service technicians who work on tires and related equipment.

"When developing ITRA training programs, we look closely at tire performance and have the opportunity to analyze a significant number of tires that failed in service. We find that the single most common cause of tire failure is underinflation. Underinflation destroys tires of nearly every type, design and application from the smallest automobile tires through commercial, aviation and large earthmover tires.

"Underinflation shortens the tread life of a tire, increases fuel consumption and negatively impacts the handling characteristics of any vehicle. It also presents serious safety risks for the occupants of the vehicle as well as other motorists in close proximity.

"For many years ITRA, along with the Rubber Manufacturers Association (RMA), Tire Association of North America (TANA), Technology & Maintenance Council (TMC) of the American Trucking Associations and others, has continuously emphasized the problems associated with underinflated tires. As indicated in one of your own surveys, approximately 36% of passenger cars and 40% of light truck tires had at least one tire that was at least 20% below the vehicle manufacturer's recommended cold inflation pressure. It is obvious from these statistics that the efforts to encourage individuals to maintain proper tire inflation have failed to make a major difference in the way the motoring public maintains their tires.

"NHTSA's Notice of Proposed Rulemaking on Tire Pressure Monitoring Systems (TPMSs) states that NHTSA crash files do not contain any direct evidence that points to low inflation pressure as the cause of any particular crash. The Rulemaking also states that even in crashes in which a flat tire blowout is reported, crash investigators cannot determine if low tire pressure contributed to the tire failure. In fact, most reports we’ve examined do not even include a designated area where tire pressures are recorded, and the remaining tires on the vehicle are rarely inspected or checked for proper inflation pressure. The condition of the tires on a vehicle have a direct impact on the handling characteristics, yet most accident investigations do not even record simple data related to tread wear and inflation. We believe this is clear evidence that the crash investigators have not been thoroughly trained in tire failure analysis. In the majority of tire failure cases we’ve examined, it is relatively easy to establish if low inflation pressure contributed to the failure.

"The lack of adequate tire failure analysis training for accident investigators is minor compared to the complete absence of education for most police officers investigating a crash scene. Once again, even the most basic information such as tire inflation pressure does not even warrant a designated space on many accident reports. It’s also relatively safe to say very few police officers have an air gauge in their squad car. Proper tire inflation has proven to be an integral component for vehicle handling characteristics and it is rarely recorded at the scene of an accident. We believe this lack of training results in the number of accidents partially attributed to low tire pressure being grossly underreported.

"Many accidents involving vehicle rollover or loss of control at exit ramps or on curvy highways are attributed to excessive speed or driver error. Underinflated tires, and the resulting reduced traction, braking and lateral stability, could play a significant role and absolutely cause the accident. It’s fair to say that if an investigator untrained in tire failure analysis finds the tires intact on the wheels and still inflated, he will likely not check the tire pressure, but will assume that the vehicle went out of control due to excessive speed or driver error. The complete lack of attention given to tires and inflation pressure has undoubtedly resulted in a significant number of accidents where poor tire maintenance caused the vehicle to lose control, but the final report does not even consider the impact of such a vital component.

"For these reasons ITRA supports the requirement for TPMSs as proposed in NHTSA Proposed Rulemaking 49 CFR Part 571. However, we believe that the indirect TPMS should not be considered. The indirect systems, as they are today, leave a lot to be desired because of the lack of ability to detect low inflation pressure in certain instances, such as if all tires are underinflated or tires on a specific axle or a certain side of the vehicle are underinflated. Once again, NHTSA’s own study showed that too many vehicles on our nation's roadways were operating with overloaded tires as the result of poor inflation maintenance. Indirect TPMSs cannot detect when all four tires on a vehicle have the same inflation pressure that is below the well-documented 80% threshold. Since tires naturally lose 1-2 psi per month and relatively few motorists check inflation pressure on a regular basis, too many motorists are operating with underinflated tires even though they do not appear 'flat' or even low. An indirect TPMS has too many limitations and exceptions to be considered a viable tire inflation pressure monitoring system.

"Although direct TPMSs are more expensive, the additional cost is minor when considering the benefits of safety, better tread wear, better fuel economy and better handling characteristics for the vehicle. By requiring a system that monitors each tire inflation pressure and notifies the driver when a specific tire has less than the minimal inflation pressure for the load of the vehicle and its contents, NHTSA will protect more motorists by preventing most catastrophic tire failures due to underinflation. The direct TPMS is simply the most logical choice because it monitors individual tire pressure and indicates which particular tire or tires are in need of attention. ITRA believes that any other system is a disservice to the motoring public unless it can effectively monitor the inflation pressure in each tire and notify the driver when one tire, or more, possesses less than 80% of the recommended inflation pressure.

"We also feel the NHTSA should explore the feasibility of some type of 'black box' technology to determine how long the tire operated after the driver was notified. This information would be extremely helpful when investigating an accident where loss of vehicle control or tire failure is involved.

"ITRA fully supports the comments sent to you by the RMA, however, there are a number of additional proposals NHTSA should consider before finalizing 49 CFR Part 571.

1) We believe that the yellow light visual warning system denoting low pressure is insufficient and it should include an audible system. We have noticed that many drivers ignore a warning light, especially on bright days. For this reason we believe a warning system should include a light and an audible alarm.

"You will note that air brake systems on large trucks have a warning device with a light and an audible alarm or buzzer when low air pressure is detected in the braking system. This type of warning system would cost very little extra and would provide a much greater margin for safety.

2) We also believe that major emphasis should be placed on making the warning systems resistant to tampering so that the light or audible alarm could not be easily disconnected or short-circuited.

3) TPMSs will be a major embellishment to the safety of motor vehicles. We believe it would be a serious mistake to use a less expensive system and encourage the NHTSA to consider the direct system or any others that may be developed in the future to provide the best protection and warning for underinflated tires.

4) It is mentioned in the Proposed Rulemaking that the direct TPMSs may be subject to damage during tire maintenance, rotating or changing the tires. Since these sensors will become mandatory on all passenger vehicles in 2003, we encourage the NHTSA to consider a design change in the wheel systems that would protect the sensors. This could be attained by designing one or more indentations in the wheel to receive the sensor and to keep it out of the path of the beads as the tire is demounted and mounted. This would create space for sensors in the future that could gather much more information, including tire temperature, the number of rotations, speed, etc. It could also provide for this information to be stored in memory as we believe the abuse a tire receives throughout its tread life can be a major cause of accidents.

5) NHTSA states that the tire manufacturers' definition of underinflation is overly strict. ITRA believes making this assumption is very dangerous and that the recommended inflation pressure must be based on the carrying capacity of the tire at specific pressures as designated by the tire and vehicle manufacturers. Admittedly, certain tires in specific applications can be operated at pressures below 80% of a manufacturer's recommend inflation pressure at certain speeds and load conditions. However, to be safe, we must assume that the vehicle will be loaded to the maximum, operated at the highest speeds and in the most extreme temperature environments.

"We believe it is extremely risky for anyone other than the automobile and tire manufacturers to specify the minimum tire pressure required to carry the axle load on any particular vehicle.

6) In regard to the symbols that would indicate an underinflated tire on the TPMS, we believe that the ISO flat tire symbol is completely ineffective and that the alternative flat tire symbol would be the best to use.

7) Whatever system is adopted, it should be universal and not specific to different manufacturers. The equipment to install, maintain and adjust the TPMS should be readily available and procedures for servicing the TPMS must be made accessible for automotive repair facilities and tire dealerships that are not associated with an original equipment vehicle manufacturer.

8) NHTSA should require a license or certification for the individual or facility responsible for installing, maintaining and adjusting the TPMS. If the ultimate goal is safety for the motoring public, then the TPMS should only be serviced by trained and qualified professionals to ensure it is in proper working order and not altered or disconnected.

"In summary, ITRA supports these positions in addition to the RMA proposals submitted through NHTSA, however, we place major importance on the additional following items:

* Direct TPMS should be used, or the most foolproof systems available at the time, and reasonable cost differentials should not be a factor.

* The warning system should include a light on the dash with an audible buzzer and be designed to make bypassing or short-circuiting the system difficult.

* Significant underinflation means any inflation pressure that is less than the pressure required to carry the actual vehicle load as determined by the tire and vehicle manufacturers.

* Installation, maintenance and adjustment of the TRMSs should only be performed by qualified personnel with the necessary training, equipment and information to ensure they are accurate and operable.

"We appreciate the opportunity to respond to this Proposed Rulemaking and stand ready to offer assistance to make the TPMSs that may be adopted the most effective available to provide greater safety for the motoring public. If NHTSA would like further explanation of any of these proposals, please contact ITRA. We will respond immediately."

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