The pre-trip inspection

Every commercial driver does one before every trip — and every CDL candidate performs one, out loud, as the first section of the skills test. Here's the full checklist zone by zone, in the order examiners expect you to walk it.

1 · Engine compartment

  • Fluid levels: oil, coolant, power steering — and no leaks underneath
  • Belts and hoses: no cracks, frays, or ballooning
  • Steering components: no loose or missing nuts, no play in linkage
  • Front suspension and brakes: springs, shocks, hoses, drum/pads condition

2 · Cab check and engine start

  • Seatbelt, mirrors, and clean windshield with working wipers
  • Gauges: oil pressure rising, air pressure building, voltmeter charging
  • Horn (city and air), heater/defroster, lighting indicators
  • Parking brake check: does the tractor hold against a gentle pull?

3 · Lights and reflectors

  • Headlights high/low, turn signals, four-way flashers, brake lights
  • Clearance lights and reflectors — clean, intact, correct color

4 · Walkaround: wheels, tires, and body

  • Tires: tread depth (4/32" steer, 2/32" elsewhere), no cuts or bulges, proper inflation
  • Rims and lug nuts: no cracks, rust trails, or shiny threads (signs of looseness)
  • Hub oil seals and axle seals: no leaks
  • Frame, crossmembers, and mudflaps: no cracks, bends, or missing parts

5 · Coupling (combination vehicles)

  • Fifth wheel: locking jaws closed around the kingpin, no gap between plates
  • Air and electrical lines: secure, no rubbing, glad hands sealed
  • Landing gear fully raised, handle secured

6 · Trailer

  • Doors, hinges, and cargo securement
  • Trailer lights, reflectors, and mudflaps
  • Trailer suspension, brakes, and tires — same standards as the tractor

7 · Air brake check (the make-or-break)

  • Static leak test: pressure drop under 4 psi in one minute (combination)
  • Low air warning activates before 60 psi
  • Tractor protection valve pops between roughly 20–45 psi
  • Spring brakes engage; service brake test — vehicle stops firmly, no pulling

How the test version is scored

The examiner walks beside you while you inspect. The rules that decide pass or fail:

  • Say it out loud. Point, name the part, state the condition: "securely mounted, not cracked, not leaking." Silent checks score zero.
  • Same route every time. Front to back, always the same order — a memorized path means nothing gets skipped under nerves.
  • The air brake check is mandatory. In most states, failing the air brake sequence fails the whole pre-trip regardless of everything else. Drill it until it's reflex.

Frequently asked

What is a pre-trip inspection?
A systematic check of the vehicle before driving — engine compartment, cab, lights, tires, coupling, trailer, and brakes. It is both a daily federal requirement for commercial drivers and the first scored section of the CDL skills test.
How long should a pre-trip inspection take?
A thorough daily inspection takes about 15–30 minutes. On the CDL skills test, plan for 25–45 minutes — examiners want to see method, not speed.
How do I pass the pre-trip portion of the CDL test?
Point at each component, name it, and say what you are checking for out loud — "securely mounted, not cracked, not leaking." Examiners score what you demonstrate, not what you silently notice. Practice the same route around the truck until the order is automatic.

The written test comes first.

Pass the general knowledge test before the skills test — practice free, no sign-up.

Start the CDL practice test