Abstract: A special accessory for traffic radar devices includes two operating routines. These routines are to be used with a programmable microprocessor which comprises a portion of the traffic radar device. The routines are designated as a stopwatch routine and an interrupt routine. The stopwatch routine controls the overall operation of the speed computation within the programmable microprocessor of the traffic radar device while the interrupt request routine causes the microprocessor to perform as a precision clock capable of measuring elapsed time.