Abstract: A system for electronically measuring the distance that a wheel has traveled can be used on a tractor-trailer combination vehicle to independently monitor mileages for the tractor and the trailer. An axle on the tractor and an axle on the trailer each has a hub odometer system which can electronically measure and store mileages for its respective axle. The system is mounted on a wheel and includes a signal generating device and a semiconductor unit. The signal generating device generates an electrical signal proportional to the number of wheel revolutions and the semiconductor unit receives, counts, and stores the electrical signals. The electrical signals are relayed to an output device. The system can also be used on other types of vehicle.