Automakers may install one of two types of tire-pressure monitors under a compromise between federal highway-safety regulators and the White House, according to the Associated Press. The agreement, outlined in February and finalized May 30, requires vehicles built after November 2003 to have a dashboard warning to alert drivers when their tires are underinflated. Congress ordered the monitors as part of strengthened tire-safety laws passed in 2000, in response to the recall of millions of Firestone tires. The National Highway Traffic Safety Administration (NHTSA) first proposed a rule that would have required "direct" monitors in each wheel that would alert drivers to low pressure. But under pressure from the auto industry, the Bush administration asked the agency to change the rule to allow an "indirect" system that would work off the antilock-braking system. Automakers favor the indirect system because it is less expensive, but safety advocates say it isn't as accurate as monitors attached to each tire. The compromise will allow vehicle makers to use either type for three years. NHTSA will study each system and write a final rule for the monitors installed in vehicles built after November 2006, according to AP. According to a NHTSA research survey, 27 percent of passenger cars on U.S. roadways are driven with one or more substantially under-inflated tires. In addition, the survey found that 33 percent of light trucks (including sport utility vehicles, vans and pickup trucks) are driven with one or more substantially under-inflated tires.