The process of inspecting revenue vehicle components on a scheduled preventive maintenance basis (e.g., engine and transmission, fuel system, ignition system, chassis, body exterior and interior, electrical system, lubrication system, braking system, air conditioning system, etc.). It includes changing lubrication fluids; replacing minor repairable unit of the above listed components; making road calls to service revenue vehicle breakdowns; towing revenue vehicles to maintenance facilities; rebuilding and overhauling repairable components; replacing major repairable units of revenue vehicles including engines, transmissions, and air conditioners, etc.