All new cars and light trucks in not just Worcester MA but in the entire US since 2008 have come equipped with a tire pressure monitoring system, or ‘TPMS’. The TPMS system detects when a tire becomes under-inflated and lights up a warning light on the dash. There are several different types of system. Some use a sensor inside the wheel which monitors the pressure and sends a wireless signal to a control module. Other system compare the tire speeds against one another and calculate tire pressure from the diameter of the tire. One last thing to keep in mind if your light comes on, it could be the spare tire that is low.