Pre-Trip Inspection of Combination Vehicles
A pre-trip inspection of a combination vehicle covers the tractor, the trailer, and the coupling between them. Candidates should know the walk-around sequence and the specific items: coupling system (fifth wheel jaws locked around the kingpin, no gap between the tractor and trailer, safety latch engaged, release handle in), air lines and electrical cord (connected, not chafed, supported so they don't drag), landing gear (fully raised, no missing parts, crank secured), trailer frame and body, doors and ties, mud flaps, lights and reflectors, tires and wheels (tread depth, sidewall condition, lug nuts, rust streaks), brake chambers and slack adjusters, and the rear impact guard. Traps: questions that ask what to check at the coupling often include items that belong elsewhere, or suggest that a visual check of the fifth wheel is enough without a tug test. Another trap is forgetting to check that the trailer is sitting level and that the air lines have enough slack to turn without pulling apart. Rule of thumb: inspect in a consistent order - start at the driver's door, work around the tractor, then the coupling, then the trailer, then back to the cab. Worked example: a rust streak from a lug nut indicates a loose or stretched stud and must be flagged, even if the nut looks tight.