Inspecting Combination Vehicles
The combination vehicle inspection is a pre-trip walk-around with a fixed order, and questions test both the items and the logic behind them. Start at the front: lights, then engine compartment (fluid levels, belts, hoses, steering), then walk the tractor checking coupling system, brake lines, suspension, and tires, then the trailer from front to rear, then the rear lights and final checks. Know the seven-step inspection concept and that you must check the coupling system (fifth wheel, kingpin, safety latch, air lines, electrical cord), landing gear (fully raised, no cracks), mud flaps, lights and reflectors, tires (tread depth, inflation, dual spacing, no cuts), and brakes including slack adjusters and push rods.
Traps: questions that ask what to check first (usually lights or the coupling depending on the walk-around convention - answer from the sequence given in your state's manual), questions about slack adjuster travel (more than about one inch of free play at the push rod means adjustment is needed), and questions about tire defects that disqualify a vehicle (tread depth below 4/32 inch on front tires, 2/32 inch elsewhere).
Rule of thumb: if you find a defect in a safety-critical item - brakes, coupling, tires, steering, lights - do not drive until it is fixed. A defect you note but ignore is worse than one you never saw.
Also know the air brake inspection is part of the pre-trip, and that you should check the trailer air lines for chafing and proper connection.