Maintaining proper tire inflation pressure has been a problem for commercial fleets ever since the invention of the pneumatic truck tire. While tires are usually the third highest cost in a fleet after labor and fuel, they are also the most difficult asset to control and maintain. The reasons for this are that although drivers are required to perform pre-trip inspections, they are not required to use a gauge to check the tires on their trucks, tractors, trailers, or buses. For the most part they believe their job is to drive the truck and deliver the freight, not maintain the vehicle. As a result, tire pressures are checked only at preventive maintenance inspections (PMs) and during scheduled trailer updates which can occur between 30 and 365 days depending upon the fleet's maintenance practices. In between these scheduled updates, mechanics usually only bump check tires to find and remove totally flat tires. Add to this that many fleets do not see their equipment regularly since they have long distance operations that prevent them from giving their tires the attention they need.