FRESNO, Calif. --If someone told you your car wasn't safe to drive, you wouldn't keep driving it, would you? Yet one in four cars has a significantly underinflated tire -- a serious safety risk. Underinflated tires contribute to thousands of crash-related injuries each year. They lead to blowouts and can negatively affect your car's handling. Plus underinflated tires waste fuel, and they wear out a lot faster.