WASHINGTON, D.C. --- The nation's top highway safety official this week cautioned motorists that hot weather and under-inflated tires are a dangerous combination. Nicole Nason, administrator of the National Highway Traffic Safety Administration, unveiled a public service announcement urging drivers to check tire pressure and tread-wear often but especially during the hot summer months. "Checking tires is particularly critical during the summer when roads are hot and families are putting a lot of miles on their cars with their vacation plans," Nason said. "Overloaded vehicles, under-inflated tires, and hot weather can all combine to possibly turn a family vacation into a horrific nightmare." Recent NHTSA research shows that hot weather can also impact the tire aging process, particularly in warm climate states. Nason said she hoped a new television ad will help encourage people to regularly check their tires for proper air pressure and monitor tread wear. "Properly maintained tires improve the steering, stopping, traction and fuel economy of your vehicle," Nason said. "Under-inflated tires or worn-down treads are a major cause of failure." Nason noted that few people take the time to check the condition of their tires, or to check whether the tire is properly inflated. A tire industry survey this year found 85 percent of drivers fail to properly check tire pressure. NHTSA estimates that crashes associated with tire problems take approximately 660 lives each year and injure 33,000 people.