From Jack Roberts, TruckingInfo:
Tire pressure monitoring and inflation systems are accepted as a proven way for fleets to manage one of their biggest consumable items and better ensure safe operation on public roadways. These systems continue to evolve, adding capabilities and functions that increase their effectiveness.
On top of monitoring, automatic tire inflation systems monitor tire pressure in comparison to a preset target pressure and automatically inflate tires whenever the detected pressure is below the target. And today there are systems available for tractor drive axles in addition to the trailer tire systems that have been around for some time.