This SAE Recommended Practice applies to speedometers, odometers, and speedometer drivestypical of passenger vehicles, buses, and trucks used for personal or commercial purposes. The method ofdetermining wheel revolutions per unit distance (3.1) and overall system design variation (3.3.3) are applicableto passenger cars only. Comparable recommendations for trucks and buses are under development. Thedata of tachometers is applicable to vehicular use, as previously described, and also to stationary and marineengines and special vehicles.