TPMS continuously monitor the pressure in the tires. The U.S. government, through the National Highway Traffic Safety Administration, requires that all passenger vehicles, light trucks and vans be equipped with a TPMS starting in model year 2008.
See also: Tires — Staying Safe on the Road
Modern tires often do not obviously show a dangerous lack of tire pressure, so these TPMS warnings provide the driver with valuable information.
The federal standard allows two different low tire pressure warning indicators or icons.
One icon is the cross-section of a tire with an exclamation mark inside.
The other icon is a top view of a vehicle with all four tires exposed.