The National Highway Traffic Safety Administration (NHTSA) this week proposed a new safety standard to warn the driver when a tire is significantly under-inflated. The proposal requires manufacturers to install a four-tire tire pressure monitoring system that is capable of detecting when a tire is more than 25 percent under-inflated and warning the driver. The standard also proposes adding a malfunction indicator that would warn the driver when the system is not working properly. For example, sometimes tires are installed on the vehicle that are incompatible with the TPMS, or sometimes other problems cause the TPMS to become inoperative. The rule would be phased in over a two-year period beginning in September 2005, and would apply to all cars, trucks and buses weighing up to 10,000 pounds.