Vehicles equipped with tire pressure monitors broadcast data that can be used to identify a vehicle as it passes a receiver and decoder placed near the roadway. This is because each tire pressure transmitter is built with a unique 32 bit ID number like the “MAC address” on ethernet adapters.
In the US, the system broadcasts on 315 MHz.
Their installation became standard in the 2008 model year.
bttt
Many cars don’t have them. It is possible to tell if a tire is low by comparing rotational data from the ABS sensing rings among the wheels. Most cars today use this system.