Class of Truck Services Operation

Truck usage, purpose, or “vocation” is categorized by type of service operation as follows:

Class A service: operation of motor vehicles on smooth, hard-surfaced highways in level country, where transmission gears are used only to accelerate the vehicle and payload from rest. Fast axle gear ratios are used.

Class B service: operation of motor vehicles on smooth, hard-surfaced highways in hilly country where numerous grades are encountered. Requires intermittent use of transmission for short periods to surmount grades. The intermediate range of axle gear ratios is used in this class of service.

Class C Service: operation of motor vehicles for dump truck service, where the vehicle operates on loose dirt, sand, or muddy roads that offer high rolling resistance. This class of service also covers operation under conditions where the transmission is used for long periods in overcoming bad road conditions on long mountain grades. Vehicle design fir this class of service usually calls for the slow range of axle gear ratios.

Class D service: operation of motor vehicles in connection with semi-trailers or trailers. This type of service is confined to smooth, hard-surfaced highways. In this service, the gross vehicle weight is the gross train weight, that is, the total weight of truck, trailer, and load.

Truck weight classifications are used to differentiate truck sizes. To fully define the vehicle, engine type and truck mission or purpose need to be known.