With normal air pressure built up and the parking brake released, roll ahead at roughly 5 mph and press the pedal firmly. The vehicle should stop without pulling to one side, feeling odd or responding late.
Exhaust parts run very hot, so they must be securely mounted, free of leaks and kept clear of the tires, the fuel system and other moving parts. Contact with those parts can damage them or start a fire, and a loose or leaking exhaust can also let poisonous fumes into the cab.
Tires of mismatched sizes are a defect to catch during the pre-trip inspection. Radial and bias-ply tires should not be used together, and front tires need at least 4/32 inch of tread in every major groove, so 2/32 inch is too little for them.
Carbon monoxide is part of engine exhaust, so broken, loose or leaking exhaust parts can let it seep into the cab, where it can cause drowsiness or even death. Low oil or coolant can damage the engine but does not send exhaust gas into the cab.
The two tire types are built differently and flex in different ways, so combining them on one vehicle can make it handle unpredictably. Driving on packed snow does not make the combination acceptable.
Before a trip you look over the engine compartment for problems you can spot or feel, such as leaks, low fluid levels, loose belts, damaged hoses and worn wiring insulation. Checking valve clearance calls for precise measurements with special tools, so it belongs to scheduled maintenance by a mechanic.
A service brake test belongs in every pre-trip inspection, since a weak brake or one that pulls to the side is far safer to discover before you leave than in traffic. The check is the driver's job, not something to save for a mechanic or a yearly inspection.
A cracked or broken spring hanger and a leaking shock absorber both weaken the suspension, which holds up the vehicle and its load and keeps the axles in place. Suspension damage like this must be repaired before the vehicle goes back on the road.
Safety comes first: an inspection helps you find defects that could cause a crash or breakdown and put you and everyone around you at risk. Inspections are also required by law and can prevent expensive repairs, but those are secondary reasons.
A front tire must have tread at least 4/32 inch deep in each major groove, and all other tires at least 2/32 inch. A tire worn below those depths is a defect that has to be corrected before the trip.
Commercial drivers are legally obligated to inspect their vehicle before every trip, however short, so that defects are found before they can endanger passengers or other road users.
To check the service brakes, roll forward slowly at about 5 mph and press the brake pedal firmly. If the vehicle pulls to one side, the pedal feels unusual or the stop is delayed, the brakes may have a problem.
The steering system links the steering wheel to the front wheels through a chain of parts that includes the steering shaft, the gear box, the Pitman arm, the drag link, the steering arms and the tie rod. Each of them should be checked for looseness, wear and damage.
These seals keep lubricant inside the wheel hub, so you confirm that none is seeping out. A leaking seal can let the bearing run short of lubricant, overheat and fail.
A walk-around covers the whole vehicle, including the steering and suspension parts: the front axle should not be cracked or bent, and the shock absorbers should not be leaking or broken. Tires, wheels, brakes, lights and couplings are checked on the same walk-around.
Tip If each listed item is something a real inspection covers, expect the all-inclusive choice to be the answer.
A wheel or rim fails inspection if a lock ring is mismatched, bent or missing, or if any clamp, spacer, stud or lug is gone. Also watch for damaged or weld-repaired rims and for rust streaks near the lug nuts, which can mean the nuts are loose.
After pumping the pedal three times, hold firm, steady pressure on it for five seconds. A pedal that stays put means the system is in good shape, while one that slowly sinks points to a leak or some other fault.
Reviewing the last inspection report is an early step of every pre-trip inspection, because it shows which defects were reported and whether the carrier certified that they were repaired or did not need repair. It is part of every inspection, not something done only when a supervisor asks or passengers are aboard.
With the key on you, no one can start the engine and drive off while you are working beneath or beside the vehicle, where a sudden move could cause serious injury.
At the front of the vehicle, the walk-around covers the front axle, the steering system (no loose, worn, bent or missing parts), the lights and reflectors (clean, working and the right color) and the windshield (undamaged, with wipers in good shape). Paint, trim and decals are cosmetic and play no part in this safety check.
Inspection continues after you pull away. Glance at the gauges regularly, and pay attention to anything you see, hear, smell or feel that could signal a developing problem.
Required equipment on a commercial vehicle includes warning devices for a stopped vehicle (for example, three reflective triangles), a fire extinguisher, and spare electrical fuses, which are unnecessary when the vehicle has circuit breakers. A spare tire, a jack, and a radio are not on the list.
Federal and state laws prohibit driving a vehicle that is not safe, so a defect found before a trip must be repaired before the vehicle is driven. Driving carefully or simply noting the problem on a report does not make an unsafe vehicle legal to operate.
The vehicle overview starts as you walk up: note the general condition and look underneath for fresh fluid leaks that may point to a mechanical problem. Starting the engine and measuring tire pressure with a gauge are later steps of the inspection.
The two tires of a dual set need space between them; if they rub against each other or against the vehicle, the friction creates heat and wear that can lead to a blowout. Contact can also be a sign of mismatched sizes or low air pressure.
The check is done with the vehicle stopped: set the parking brake, then gently try to pull forward against it in a low gear to make sure it keeps the vehicle from moving. Trying it at speed or on a downhill stretch would be dangerous if the brake did not hold.
Part of confirming a bus is safe is reviewing the last driver's inspection report. Sign it only after you have verified that each defect on it was fixed, or that a repair was found to be unnecessary.
Rust around the lug nuts is a common clue that they have loosened. Welding does not make a cracked wheel or rim safe, and a wheel missing even one lug nut is defective, so either problem must be repaired before the vehicle is driven.
A healthy engine builds normal oil pressure just seconds after it starts. If the gauge stays low, turn the engine off at once, because running without lubrication can ruin it quickly.
Front tires, which do the steering, must keep a minimum of 4/32 inch of tread in each major groove; other tires may go as low as 2/32 inch. Deeper tread up front helps you keep steering control.
Federal safety rules call for a set of three red reflective warning triangles. Whenever a breakdown leaves you stopped on or beside the road, put them out promptly so approaching drivers are warned in time.
Drivers who work for an interstate carrier must fill out a written inspection report when each shift ends, covering every vehicle they operated that day.
Every question in this set has its own page with the correct answer and an explanation.
