Method and apparatus for tire pressure monitoring

Motor vehicles are supported by inflatable tires having a desired inflation pressure. Improper inflation of a tire can lead to poor gas mileage and increased tire wear. Maintaining tire inflation within an acceptable range can alleviate these issues. To do so however, requires frequent measuring of tire pressure and evaluation of whether that pressure lies within an acceptable range. Moreover, tire pressure will also vary according to temperature and vehicle load. The relative speed of each of the tires of a vehicle is monitored as an indication of the operating state of the vehicle, wherein if the vehicle is not operating in one of a number of predetermined states, the relative speed is monitored as an indication of relative pressure of the vehicle tires, and further wherein differences in relative speed not related to the predetermined states, and not related to differences in relative pressure, are accounted for. In addition, a single tire pressure sensor is employed to account for over or under inflation of substantially equal proportion in the tires.