WASHINGTON (Aug. 29)—More than one in four passenger cars and one in three light trucks in the U.S. are being driven on one or more "substantially" underinflated tires, according to a new study by the National Highway Traffic Safety Administration. This is the first such government study of the situation in more than 20 years. For this study, underinflated meant any tire operating at 8 psi or more under the recommended inflation pressure, NHTSA said. The study is based on information gathered on 11,530 passenger vehicles during a 14-day period in February. The information was collected from motorists at 300 service stations in urban, suburban and rural settings across the country. The data show 27 percent of cars monitored had at least one underinflated tire, and 32 percent of light trucks—including sport utility vehicles, vans and pickups—were in the same plight. Looking at the data breakdown, the study shows light truck owners are worse at maintaining their tires than passenger car owners, and owners of older vehicles are worse at maintaining proper tire pressure than are operators of newer vehicles. NHTSA estimates that 49 to 79 deaths and 6,585 to 10,635 injuries could be prevented annually if all vehicles were equipped with tire pressure monitoring systems.