Vehicle Inspection: The Three-Part Walk-Around
The Vehicle Inspection domain tests the three-part inspection cycle - pre-trip, en route, and after-trip - and the exact defect limits an examiner expects you to state from memory rather than gesture at.
What the pre-trip covers
- Engine compartment: oil and coolant level, power steering fluid, belts, hoses, and any leaks.
- Walk-around: headlights, turn signals, reflective tape, tires, wheels, rims, suspension, brake lines, coupling devices, mud flaps.
- Cab and controls: mirrors, horn, wipers, gauges, heater and defroster, steering play, service brake and parking brake.
Defect limits the test scores
- Steer tires need 4/32 inch of tread; every other tire needs 2/32 inch. No cuts, bulges, or exposed cord.
- Rust streaks or shiny threads around lug nuts mean loose nuts or worn studs.
- Slack adjuster: with the brakes released, the pushrod should not move more than about one inch.
- Air loss with the engine off: no more than 3 psi per minute with brakes released, 4 psi per minute with brakes applied.
Worked example
A tractor-trailer's air gauge drops 5 psi in one minute with the brakes released and the engine off. The released limit for a combination is 3 psi per minute, so this fails. It is an out-of-service defect, not something you note and drive on. You record it on the report and do not move the vehicle until it is repaired.
Traps that cost marks
- Quoting the 4 psi applied figure when the question describes the released test.
- Forgetting the after-trip report and the driver's signature on it.
- Assuming a known defect lets you drive to the nearest shop.
- Saying the pre-trip is done once and never repeated; you also inspect en route.