Cabover (Cab-Over-Engine, COE): Truck or tractor design in which the cab sits over the engine on the chassis.
Cargo Weight: Combined weight of all loads, gear and supplies on a vehicle.
Cartage Company: Company that provides local (within a town, city or municipality) pick-up and delivery. 
Cast Spoke Wheel: Wheel with five or six spokes originating from a center hub. The spoked portion, usually made of cast steel, is bolted to a multiple-piece steel rim (see Demountable Rim; Disc Wheel).
CB (Citizens Band Radio): Two-way radio for which no license is required by the Federal Communications Commission (FCC). Long beyond its heyday in the ’70s, CB is still used by truckers and motorists for everything from traffic condition reports to emergency calls to idle chatter.
CDL (Commercial Driver’s License): License which authorizes an individual to operate commercial motor vehicles and buses over 26,000 pounds gross vehicle weight. For operators of freight-hauling trucks, the maximum size which may be driven without a CDL is Class 6 (maximum 26,000 pounds gross vehicle weight).
CE (CF, LP): Distance from back of a truck’s cab to the end of its frame.
CFC: Chlorofluorocarbon.
CG (Center of Gravity): Weight center or balance point of an object, such as a truck body. Calculated to help determine optimum placement of truck bodies on chassis.
Chassis Weight (Curb Weight, Tare Weight): Weight of the empty truck, without occupants or load.
CNG: Compressed natural gas.
COFC (Container On Flat Car): Method of moving shipping containers which involves transporting them on railroad flat cars.
Common Carrier: Freight transportation company which serves the general public. May be regular route service (over designated highways on a regular basis) or irregular route (between various points on an unscheduled basis).
Compensated Intracorporate Hauling: Freight transportation service provided by one company for a sister company.
Container (Shipping Container): Standard-sized rectangular box used to transport freight by ship, rail and highway. International shipping containers are 20 or 40 feet long, conform to International Standards Organization (ISO) standards and are designed to fit in ships’ holds. Containers are transported on public roads atop a container chassis towed by a tractor. Domestic containers, up to 53 feet long and of lighter construction, are designed for rail and highway use only. 
Container Chassis: Single-purpose semitrailer designed to carry a shipping container.
Contract Carrier: Company that transports freight under contract with one or a limited number of shippers.
Converter Dolly (Dolly): Auxiliary axle assembly equipped with a fifth wheel (coupling device), towed by a semitrailer and supporting the front of, and towing, another semitrailer.
Cube (Cubic Capacity): Interior volume of a truck body, semitrailer or trailer, measured in cubic feet.