Unintended Consequences Could Hit Our Tires

The National Highway Traffic Safety Administration has mandated the installation of tire pressure monitoring systems in new vehicles beginning with the 2004 model year. The big question: will this "safety" measure actually result in diminished safety for the average motorists? Many tire manufacturers think so, and now they have a poll to back them up.

A new survey just released shows that the devices will cause American motorists to check their tire pressure less frequently, and that could result in a decline in safety. The survey, sponsored by the Rubber Manufacturers Association, found the frequency of U.S. motorists' checking their tire pressure will likely drop by nearly 25 percent in vehicles equipped with tire pressure monitoring systems (TPMS). Even more troubling is the fact that motorists who exhibit the most responsible tire-pressure-checking behavior -- checking pressure at least once a month -- would likely show a significant decline in tire maintenance.

"The tire industry has been working for decades to encourage motorists to check their tire pressure regularly," said Donald B. Shea, RMA president and CEO. "But our survey shows that many drivers will reduce or stop checking their tire pressure because they may incorrectly believe that their tires are properly inflated when the tire pressure warning light is off."

The NHTSA tire pressure sensor regulation issued last year requires that tire pressure monitors warn motorists when tire pressure falls 25 or 30 percent below the vehicle manufacturer's recommended level. Tire makers insist this is not the best way to address a potential safety threat.

"The trigger point for a tire pressure monitoring system to warn a driver must be when the tire is overloaded for its inflation pressure," Shea said. "If tire pressure monitoring systems do not provide an adequate warning to motorists, and drivers become more complacent about proper tire care, the risk of tire failures may increase."

The big culprit in the issue is underinflation, which occurs naturally in auto tires in general use. When tires are underinflated it causes excessive heat buildup that, over time, can result in hidden damage that can cause tire failure.

One year ago, RMA petitioned NHTSA to adopt a new safety regulation requiring motor vehicle tires to have a "reserve inflation pressure," but NHTSA has not yet responded to the RMA petition. The petition included data on 100 vehicle/tire combinations, which when outfitted with the proposed monitoring systems, showed over 70 percent would fail to warn motorists before the vehicle's tires reach a point when the inflation pressure can no longer carry the load.

The tire industry association believes a reserve pressure rule will ensure that TPMS will provide drivers with a timely warning when tires are underinflated. Under the proposal, a vehicle's tires would be required to have a recommended inflation pressure that would be sufficient to carry the vehicle's maximum load even if the tire loses a significant amount of pressure. This would provide consumers with a vital safety net since only 14 percent of motorists properly check their inflation pressure, according to a February 2003 RMA survey. But auto manufacturers are expected to resist this proposal since it might force them to equip their vehicles with larger tires than might currently be required.

Echoing the tire industry's concerns about tire pressure monitoring systems, a National Transportation Safety Board (NTSB) crash investigation of 15-passenger vans concluded that NHTSA's tire pressure monitoring standard "is insufficient to warn van drivers of potentially unsafe low pressures." NTSB is recommending that NHTSA adopt "more stringent detection standards" for low tire pressure than is currently mandated for large passenger vans.

One thing is certain: the controversy will be on-going. In August a U.S. Appeals Court decision overturned the TPMS rule and ordered the agency to craft a new one. The court ruled the agency inappropriately permitted certain types of tire pressure monitoring systems to be installed on new vehicles.

"We want to work with the government so the tire pressure monitoring systems promote safety," Shea said. "A tire pressure monitoring system can be an effective safety tool for motorists only if it provides a timely warning."


Driving Today Managing Editor Jack R. Nerad writes frequently on highway safety issues.