According to astudy, released today by the Department of Transportation, 32% of light trucks, including sport utility vehicles and vans, are driven with one or more substantially under-inflated tires. Prompted by the survey results, U.S. Transportation Secretary Norman Y. Mineta today urged motorists to check their tire pressure and inflate them properly before the Labor Day weekend.

"It is vitally important to safety to carefully monitor tire pressure on a regular basis," Mineta said. "Driving with substantially under-inflated tires can lead to crashes and tragedy, in addition to reducing fuel efficiency and shortening tire life."

Mineta added that a radial tire can lose much of its air pressure and still appear to be fully inflated.

To help vehicle owners better monitor the air pressure in their tires, the National Highway Traffic Safety Administration (NHTSA) last month proposed a new federal motor vehicle safety standard that would require the installation of tire pressure monitoring systems in new passenger cars and light trucks. The proposed requirement would also cover buses and multipurpose vehicles with a GVW rating of 10,000 pounds or less.

For purposes of the survey, a tire was considered under-inflated at 8 psi or more below the vehicle manufacturer's recommended inflation pressure. This is 25% of a common recommended cold inflation pressure of 32 psi.