Applying Pressure to Boost Tire Safety
In response to consumer and lawmaker outrage over the accidents, injuries and deaths blamed on faulty and since- recalled Firestone tires, the federal government has mandated that tire pressure monitors be phased in as standard equipment on cars and light trucks over three years, beginning Nov. 1, 2003.
Rules set by the National Highway Traffic Safety Administration will require manufacturers to install monitors on 10% of their vehicles the first year, 35% the second and 65% the third, before reaching 100% in 2006.
The monitors must activate a dashboard warning when a tire is low on air; auto makers may use one of two systems to meet the rule. In 2006, regulators are expected to eliminate the choice and require all auto makers to use the same type of monitor.
The so-called direct system has air pressure monitors on each wheel and is designed to alert the driver when pressure in any tire drops by more than 25%. The sensors typically convey information to the dashboard monitor via low-frequency radio waves.
The indirect system uses sensors from the vehicle’s anti-lock braking system to measure the rotation of all four tires and can detect whether any is significantly different from the others. The indirect system activates a warning when pressure in one tire drops 30% below the pressure of at least one other, but does not specify which tire is low.
NHTSA regulators favor the direct system--which costs at least $66 per vehicle, according to agency estimates, versus as little as $13 or less for the indirect type--because it alerts the driver when any tire loses air. With the indirect system, NHTSA says, there is no warning if all four tires lose an equal amount of air pressure, even if the loss is greater than 30%.
The Bush administration, however, has countered that using the indirect system would lower the cost and increase the rate of installation of anti-lock braking on new vehicles (currently at 67%). Although auto makers support the cost argument, none has promised to increase anti-lock brake installation.
NHTSA’s compromise was to allow both systems until Nov. 1, 2006, when the agency will require monitors on all new vehicles. NHTSA will issue a final rule by Nov. 1, 2005, using data collected on both systems to decide whether to select one of those already in use or to recommend another.
Tire pressure monitors were one requirement of TREAD, the Transportation Recall Enhancement, Accountability and Documentation Act, passed by Congress in 2000 after investigations into tread failure on Firestone tires. Low tire pressure was cited as a cause of tread failures that contributed to accidents that claimed at least 271 lives.
NHTSA’s compromise plan quickly drew complaints. Joan Claybrook, president of Public Citizen and a former NHTSA administrator, said the group would sue to require the direct system, which it says will save more lives.
The Rubber Manufacturers Assn., a trade group for tire makers, said a tire running at 25% to 30% below its recommended air pressure cannot carry a full load and is more apt to fail.
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Rick Popely is an automotive writer at The Times’ sister paper, the Chicago Tribune.
