Side, rear, coupling system and trailer

Walking down the side, you check lenses and reflectors, mirrors, battery, fuel tank and frame, then the rear lights. If you test in a combination vehicle, you also inspect the air and electric lines, the coupling (fifth wheel, pintle hook or tow hitch), the locking devices, the landing gear and the reflective tape.

Side of the vehicle

Lenses and reflectors (vehicle and, on a combination, trailer): lenses and reflectors are the proper color, clean, not broken and not missing. Reflectors help other drivers see you.

Traffic monitoring devices: side mirrors show traffic beside and behind you, especially in blind spots. Mirrors are clean and not cracked; brackets are not bent, mounted securely, no missing parts. Cameras (if equipped) are clean so you can see from inside.

Battery: damage to batteries, wiring or an electric motor can cause a breakdown or a short circuit that starts a fire. Wherever it is located: batteries are secure (if visible); connections are tight with no heavy corrosion; cables and lines are secure, not cracked or worn; the battery box, cover or door is secure. If the batteries cannot be seen, tell the examiner and describe what you would check.

Fuel tank / DEF tank: leaks are a fire hazard, and fuel on the road is very slippery for other traffic. Check that the tank (and any DEF tank) is firmly mounted, its cap is on tight, and neither the tank nor its lines leak.

Frame(s): loose or cracked frame members can cause wandering, rollover and total loss of control; holes in the cargo area can let cargo fall out. Look for cracks, broken welds, holes or other damage in the frame (and trailer frame), and cracks, breaks or holes in the cargo floor. On a trailer, check that the tandem release lever and locking pins are secure.

Say: I'm checking that the fuel tank is securely mounted, the cap is tight, and there are no leaks.

Rear of the vehicle or trailer

At the rear, lenses and reflectors are the proper color, clean, not broken and not missing. On a combination vehicle you only inspect the rear of the trailer.

Air and electric lines (combination only)

These lines carry air and electricity from the power unit to the trailer. Losing air to the trailer means partial or total loss of trailer braking, and low air makes the trailer spring brakes come on suddenly. Losing the electric connection on electric brakes means total loss of trailer braking. Damaged electric lines mean no turn or brake lights — other drivers cannot see what you are doing, which is very dangerous at night.

• Air and electric connectors on both the power unit and the trailer are seated and sealed, not damaged, and locked in place. You must inspect both ends to get credit.
• Air hoses and electric lines are not cut, cracked, chafed, spliced, taped or worn (steel braid or wire must not show). Listen for air leaks (air brake systems).
• Lines are not tangled, crimped or pinched, and not dragging on vehicle parts or the ground.

Say: I'm checking that the glad hands are seated and sealed and locked in place, and the lines are not cut, chafed, spliced, or taped, and not dragging.

Fifth wheel combinations

Study the coupling type of the vehicle you will test in: fifth wheel, pintle hook, or another type. A bad coupling can cause handling problems, rollover, or the trailer separating from the tractor.

Fifth wheel skid plate (the plate the trailer rests on, which holds the kingpin): securely mounted to the fifth wheel platform; no cracks, breaks or heavy wear; properly lubricated if applicable.

Kingpin, apron and gap: the kingpin is in place and not bent, damaged or worn. The visible part of the apron (the plate around the kingpin that sits on the fifth wheel) is not bent, cracked or broken. The trailer lies flat on the skid plate with no gap between apron and fifth wheel. Lubricated if applicable.

Locking and safety devices (fifth wheel): look into the fifth wheel gap and check that the locking jaws or lever are fully closed around the kingpin, and check for play between kingpin and jaws. The release arm is in the engaged (locked) position and the safety latch is in place, if equipped. On a sliding fifth wheel, the locking pins are not damaged and are fully engaged.

Say: I'm checking that the locking jaws are closed around the shank of the kingpin, there is no gap between the apron and the fifth wheel, and the release arm is locked.

Pintle hook, tow hitch and other couplings

Pintle hook (the hook the trailer drawbar ring locks into): securely mounted to the vehicle frame; no loose or missing parts (mounting bolts, nuts, pins, brackets, clamps); no cracks, breaks or heavy wear.

Drawbar ring (eye) and tongue: the ring is not bent, twisted or worn; it is secured to the tongue with no loose or missing bolts, broken welds or cracks. The tongue has no dents, twists, cracks or broken welds and can carry the load. If the tongue extends, its bolts, locking pins and cotter pins are in place.

Tow hitch (receiver hitch and trailer ball): securely mounted to the frame; check the sway bar/control if equipped; no loose or missing parts (including the ball); no cracks, breaks or heavy wear.

Trailer coupler and tongue: the coupler is not bent, twisted or worn, and is secured to the tongue with no loose or missing bolts, broken welds or cracks. The tongue checks are the same as above.

Locking and safety devices (other couplings): the lock or latch has no missing or broken parts and the release lever or latch is locked and secure; safety pins and cotter pins are in place; safety chains or cables are secure, crossed, with no kinks and no excessive slack; breakaway cables must be connected (engaged).

Other coupling types: systems vary. If yours is different, describe to the examiner how it works and what you are checking.

Trailers only: landing gear and reflective tape

Landing gear holds up the front of the trailer when it is not coupled. It must be raised so it does not hit the ground while driving and clears the back of the tractor in turns. The crank handle must be secured so it cannot swing out and hit other traffic. Damaged supports can let a dropped trailer tip or fall.

• Landing gear is fully raised, no missing parts, crank handle secured, support frame and landing pads not damaged.
• If power operated, check for air or hydraulic leaks.
• On a tractor semi-trailer, the fifth wheel (fixed or sliding) is positioned so the tractor frame clears the landing gear in turns.

Reflective tape: tape on the sides and rear of the trailer helps others see you. Check that it is present and firmly attached. Reflective tape is required only on trailers, though some states also require it on school buses.

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.