It is essential that speedometers be calibrated accurately so that advisory speeds will be uniform throughout the state.

Calibrate the speedometer for recording of speed. The accuracy of the odometer for recording distance should be checked against a measured distance. Calibration for speed can be done easily with a radar speed meter or by timing the car over a measured distance. The speedometer should be checked for each 5 mph interval over 20 mph, and several test runs should be made for each speed so that an average value may be obtained.