WASHINGTON - A recent nationwide survey by the Rubber Manufacturers Association (RMA) shows 55 percent of vehicles have at least one under-inflated tire and only one in six vehicles has four properly inflated tires.

Other findings revealed:

• 15 percent of vehicles have at least one tire under-inflated by 8 psi.

• 20 percent of vehicles have at least one tire under-inflated by 6 psi.

• 31 percent of vehicles have at least one tire under-inflated by 4 psi.

However, compared to a similar survey last year, "motorists showed some improvement in tire care habits," according to RMA officials. "This year, almost twice as many vehicles had four properly inflated tires as had last year."

The survey's best performing cities, those with a higher percentage of vehicles with four properly inflated tires, were Honolulu, Baltimore, Boston, Providence, and Charlotte. At the bottom of the list were Dallas/Ft.Worth, Los Angeles, Orlando, San Antonio, and Birmingham, according to the RMA.

Properly inflated tires can improve fuel efficiency by 3.3 percent and save nine cents per gallon at the pump, according to the U.S. Department of Energy. Approximately 1.2 billion gallons of fuel are wasted each year by U.S. motorists driving on under inflated tires.

The National Highway Traffic Safety Administration (NHTSA) estimates that under-inflated tires contribute to more than 600 fatalities and 33,000 injuries each year.