You've heard it before. Check your tire pressure regularly. Now federal safety experts say at least one out of four vehicles on the road have at least one tire that is seriously under inflated. Officials say that could mean the difference between life and death on the highway. Tire experts recommend checking your tire pressure every other trip to the gas pump. You can easily find how many pounds per square inch or P.S.I. your tires require. According to the experts, over 600 people die each year in the U.S. because of under inflated tires and over 30,000 are injured.