Study guide
Every safe trip in a commercial vehicle starts before the wheels move, with an inspection routine thorough enough to catch the defect that would otherwise find you at highway speed. This chapter covers the three types of inspection, the seven-step pre-trip routine, the specific defects the exam expects you to recognize, and the fundamentals of controlling and shifting a heavy vehicle.
Why You Inspect and the Three Types of Inspection
Safety is the most important reason you inspect a commercial vehicle: a defect found in the yard is a repair ticket, while the same defect found at highway speed can be a crash. Inspection is also a legal duty under federal and state rules, and roadside inspectors can place a defective vehicle out of service until it is repaired. The manual describes three types of inspection. The pre-trip inspection happens before every drive; you work through a set routine to find anything that could cause trouble on the road. The en-route inspection happens during the trip: watch your gauges for signs of trouble, use your mirrors, and stop periodically to check critical items such as tires, wheels and rims, brakes, lights, and cargo securement devices. Cargo has its own inspection schedule, covered in chapter four. The post-trip inspection happens at the end of the day or run and often includes a written or electronic vehicle inspection report listing any defects you found. That report matters more than it looks: the mechanic and the next driver rely on it, and the motor carrier must repair anything on it that affects safety before the vehicle is dispatched again. Picture a driver named Lena finishing a shift and noting a soft brake pedal on her report. The fix happens overnight in the shop instead of tomorrow afternoon on a downgrade. The exam rewards drivers who treat inspection as a continuous loop — before, during, and after every trip — rather than a one-time chore.
The Seven-Step Pre-Trip Routine
The manual organizes the pre-trip inspection into seven steps, and doing them in the same order every time means nothing gets skipped. Step one is the vehicle overview: as you approach, look for leaning, fresh oil or coolant puddles underneath, and body damage, then review the last vehicle inspection report to verify that reported defects were repaired. Step two is the engine compartment check: engine oil level, coolant level, power steering fluid, belt condition, and any leaks or worn electrical insulation. Step three is to start the engine and inspect inside the cab: watch the gauges — oil pressure should come up within seconds of starting — and check the steering wheel, clutch, mirrors, wipers, lights, horn, heater and defroster, and the condition of your safety belt. This is also when you confirm the required emergency equipment is aboard. Step four: turn off the engine, take the key with you, and check the exterior lights, starting with the headlights on low and high beam and the four-way flashers. Step five is the walkaround: turn on the left turn signal, then move around the vehicle in a set pattern, cleaning and checking every light and reflector, and examining tires, wheels, suspension, brakes, fuel tanks, frame, and doors as you go. Step six: check the signals you could not see earlier — right turn signal and brake lights. Step seven: start the engine and check the brake system. With hydraulic brakes, pump the pedal three times, then hold firm pressure for five seconds; a pedal that keeps sinking means a leak. Test the parking brake by gently pulling against it in a low gear, then test the service brakes at about five miles per hour, feeling for pulling or delayed response.
Tires, Wheels, Steering, and Suspension
Tires cause more roadside failures than almost any other component, so learn the numbers. Front steering-axle tires need at least 4/32 inch of tread depth in every major groove; all other tires need at least 2/32 inch. Look for cuts, bulges, tread separation, fabric showing through the rubber, and mismatched sizes. Radial and bias-ply tires must never be used together, dual tires must not touch each other or any part of the vehicle, and every valve stem should be undamaged with its cap in place. On wheels and rims, rust streaks trailing away from lug nuts often mean the nuts are loose — and after any tire change, stop a short way down the road and re-check tightness, because nuts loosen as new mounts seat. Cracked or bent rims are dangerous, and a rim repaired by welding is never acceptable. On the steering system, look for missing nuts, bolts, and cotter keys, bent or damaged parts, and power steering leaks. Steering wheel play of more than about ten degrees — roughly two inches of rim movement on a twenty-inch wheel — makes the vehicle hard to steer and is a reportable defect. The suspension carries the load, so its defects are serious: cracked or broken spring hangers, missing or broken leaves in a leaf spring — if a quarter or more of the leaves are missing, the vehicle goes out of service — sagging springs, leaking shock absorbers, and air suspension leaks. Imagine a driver named Karim spotting a bright rust trail on two lug nuts during his walkaround. Five minutes with a wrench and a torque check beats a wheel separating on the interstate.
Brakes, Lights, and Emergency Equipment
Brake checks continue during the walkaround. Look for cracked drums, brake shoes or pads soaked with oil or grease from a leaking seal, and linings worn dangerously thin — many inspection checklists use about a quarter inch as the minimum. Brakes are the one system where a defect can never ride along: any brake problem stops the trip until it is fixed. Lights and reflectors must be clean and working: headlights, brake lights, turn signals, four-way flashers, clearance and identification lights on larger vehicles, and the side and rear reflectors. Color conventions show up on the exam — red lights and reflectors face the rear, while amber faces the front and sides — because a driver seeing amber at night knows the vehicle is pointed toward them. Federal rules also require specific emergency equipment on commercial vehicles: a properly charged and rated fire extinguisher, spare electrical fuses unless the vehicle uses circuit breakers, and warning devices for a parked or disabled vehicle, most commonly three reflective triangles, though flares or fusees are permitted in some circumstances and states. Smart drivers add tire chains where winter travel requires them, basic tools, and a list of emergency contacts and accident-reporting steps. When Lena's pre-trip found a dark brake light, she swapped the bulb in the yard in two minutes. The alternatives were explaining the defect to a roadside inspector or being invisible to the driver behind her at the worst possible moment.
Basic Control: Backing, Shifting, and Retarders
Basic control begins with smoothness: accelerate gradually so the vehicle does not jerk, steer with both hands on opposite sides of the wheel, and push the brake pedal down progressively rather than stabbing it. Backing is the highest-risk low-speed maneuver because you can never see everything behind you. Avoid backing whenever possible — park so you can pull forward to leave. When you must back, back and turn toward the driver's side, even if it means driving around the block to set it up, because you can watch the rear of the vehicle out your window instead of guessing across the cab through mirrors. Use a helper whenever you can, agree on hand signals before starting — especially the signal for stop — and back slowly. The habit called GOAL, short for Get Out And Look, means walking back to check your path before and even during the maneuver. On shifting: most heavy manual transmissions require double clutching — clutch in, shift to neutral, clutch out, let engine speed adjust, clutch in, shift into the next gear. There are two ways to know when to upshift: engine rpm, using the tachometer and the operating range in the vehicle manual, and road speed, learning which speeds each gear covers. Downshift before you need the lower gear — before entering a curve and before starting down a hill, never partway down. Retarders — exhaust, engine, hydraulic, or electric — slow the vehicle without the service brakes and reduce brake wear. But when the drive wheels have poor traction, a retarder can cause a skid, so turn retarders off on wet, snowy, or icy roads. Some communities restrict engine braking because of noise, so watch for posted signs.
Key terms
- Pre-trip inspection
- — The systematic check of a commercial vehicle performed before every drive to find problems that could cause a breakdown or crash.
- Vehicle inspection report
- — The written or electronic post-trip record of defects a driver found, which the carrier must act on before the vehicle runs again.
- En-route inspection
- — Checks made during a trip using gauges, mirrors, and periodic stops to examine tires, brakes, lights, and cargo securement.
- Tread depth
- — The depth of a tire's grooves, with minimums of 4/32 inch on front steering tires and 2/32 inch on all other tires.
- Steering wheel play
- — Free movement of the steering wheel before the wheels respond; more than about 10 degrees, or two inches on a 20-inch wheel, is a defect.
- Leaf spring
- — A stack of curved metal strips that suspends the vehicle's weight; missing or broken leaves are serious suspension defects.
- Brake lining
- — The friction material on brake shoes or pads, which must not be dangerously thin or contaminated with oil or grease.
- GOAL (Get Out And Look)
- — The backing habit of physically walking behind the vehicle to check the path before and during the maneuver.
- Double clutching
- — The shifting technique of using the clutch twice per gear change, passing through neutral while engine speed adjusts.
- Tachometer
- — The gauge showing engine revolutions per minute, used along with road speed to time upshifts and downshifts.
- Retarder
- — An exhaust, engine, hydraulic, or electric device that slows the vehicle without the service brakes; it should be off on slippery roads.
- Reflective triangles
- — The three-piece set of warning devices carried to mark a stopped vehicle for approaching traffic.
Exam tips
- Memorize the tread depth pair cold: 4/32 inch on the front steering tires, 2/32 inch everywhere else. Test writers love to swap the two numbers in wrong answers.
- Learn the seven inspection steps in order — overview, engine compartment, inside the cab with engine on, lights, walkaround, signal lights, brake checks. Questions often ask what happens in a specific step.
- Rust streaks radiating from wheel nuts signal loose nuts, and a recently changed tire should have its lug nuts re-checked shortly after the trip begins.
- For backing questions, the safe pattern is: avoid backing when possible, back toward the driver's side, use a helper with an agreed stop signal, and get out and look.
- Retarder questions usually test one fact: turn the retarder off whenever the road is wet, snowy, or icy, because it can skid the drive wheels.