To comply with the regulation, which has its roots in the Firestone tire recall of 2000, automakers most likely will attach tiny sensors to each wheel that will signal if a tire falls 25 percent below the recommended inflation pressure. If any one of the four tires is underinflated, the sensors set off a dashboard warning light.
Automakers will begin implementing the technology in September. The National Highway Traffic Safety Administration estimates the upgrade will cost manufacturers between $48.44 and $69.89 per vehicle.
The government said underinflated tires hurt a vehicle's fuel economy and can increase stopping distances, increase likelihood of tire failure and lead to skidding on wet surfaces.
All new four-wheel vehicles weighing 10,000 pounds or less will be required to be equipped with the systems by the 2008 model year. The regulation affects passenger cars, sport utility vehicles, pickup trucks and minivans.
NHTSA estimates that 120 lives a year will be saved when all new vehicles are equipped with the systems.
The regulation was proposed last September. Tire manufacturers have questioned whether the warning system would signal low pressure early enough. Automakers have raised concerns that motorists may ignore the lights if they appear too frequently.
Donald B. Shea, president and chief executive of the Rubber Manufacturers Association, the trade group that represents tire makers, said, "Unfortunately, this regulation may give motorists a false sense of security that their tires are properly inflated when they may be significantly underinflated."
Eron Shosteck, a spokesman for The Alliance of Automobile Manufacturers, which represents nine automakers, said about 18 percent of their vehicles already have the technology. It first appeared in the 1997 Chevrolet Corvette and is currently used in some luxury vehicles.
"We're gratified that there's a final rule which allows us to continue the implementation of the technology as we've been doing," Shosteck said.
Congress, seeking ways to prevent SUV rollovers after more than 10 million Firestone tires were recalled beginning in August 2000, sought the warning devices in The Transportation Recall Enhancement, Accountability and Documentation Act.
NHTSA originally issued a rule in December 2001 that would have required vehicles made after November 2003 to have dashboard lights warning drivers if their tire pressure was low.
But Public Citizen and other consumer groups sued the government agency, arguing the rule weakly allowed automakers to choose between cheaper "indirect" monitors, which operate off the antilock braking system, or "direct" systems, which have monitors attached to each wheel.
A federal appeals court in New York agreed with the consumer groups and tossed out NHTSA's rule in August 2003, leading to the new process of issuing the regulation.
Joan Claybrook, the president of Public Citizen and a former NHTSA administrator, said she would prefer that motorists get quicker warnings about low tire pressure.
The rule requires the system to warn the driver within 20 minutes of additional travel within a speed range of about 30 mph to 60 mph. Claybrook said motorists driving locally at lower speeds might be delayed in receiving the dashboard warning.
"It's not exactly what we hoped but I think that it will work," Claybrook said.
By Ken Thomas