Pre-Trip Inspection of Combination Vehicles
Pre-Trip Inspection of Combination Vehicles
The pre-trip domain tests a systematic walk-around that proves the tractor, trailer, coupling, brakes, and cargo are ready. The exam emphasizes combination-specific items: fifth wheel, air lines, electrical cord, landing gear, trailer frame and body, and the trailer brake test.
What to check
- Coupling: fifth wheel mounted, jaws closed, safety latch engaged, apron and kingpin sound, no gaps.
- Air lines and electrical cord: connected, sealed, not chafed or dragging, properly supported.
- Landing gear: fully raised, handle secured, no damage.
- Trailer: frame, body panels, doors, hinges, roof, mud flaps, lights, reflectors, tires, wheels, rims, lug nuts, brakes, suspension.
- Tractor: steering, tires, brakes, lights, mirrors, horn, wipers, fluids, belts.
- Cargo: securement devices, load limits, nothing obscuring lights or plates.
- Air brake test: charge to governor cut-out, shut off engine, check leak rate, apply service brakes, check trailer spring brakes.
Worked example
You hear an air leak near the glad hands. You spray soapy water on the couplers. Bubbles appear at the service glad hand. The seal is damaged. You replace the seal, reconnect, and recheck. A leak here can prevent the trailer from charging and can cause the spring brakes to drag or set. The correct response is repair and retest, not to assume it will hold for a short trip.
Traps
- Inspecting only the tractor.
- Missing a cracked glad hand seal.
- Checking lights but not reflectors.
- Forgetting the trailer brake test.
- Overlooking cargo securement because the load looks heavy.
Key points
- Use a fixed walk-around order.
- Fifth wheel, lines, gear, and lights are combination-specific.
- Leak-test the air system, including the trailer.
- Check tires, brakes, and suspension on both units.
- Cargo securement is part of pre-trip.