Vehicle Inspection and Basic Control
The inspection sequence
A pre-trip inspection must be systematic, not random. Walk around the vehicle the same way every time: overall overview and leaks, engine compartment (fluids, belts, hoses, steering), lights and reflectors, brake system and air pressure buildup, suspension and steering components, tires and wheels, then coupling devices and trailer. State what you are checking and what a defect looks like.
Air brake tests
With a fully charged system and the engine off, a static leak test should show no more than about 3 psi per minute on a single vehicle or 4 psi on a combination; with the service brake held fully applied, the allowance is about 4 psi (6 psi for a combination). The low-air warning must activate before pressure falls below 60 psi, and the spring brakes should set somewhere between 20 and 45 psi as pressure bleeds off.
Basic control
Back in the direction that gives you the best view, using both mirrors, and get out and look if you are unsure. Longer wheelbases and sharp turns produce more off-tracking - the rear wheels cut a shorter path than the front wheels - so swing wide on right turns and watch the right mirror. Shift before a hill, do not coast with the clutch in, and keep both hands on the wheel.
Traps
Questions ask whether to test with the engine running (no), whether pumping the pedal rebuilds air (no), and whether off-tracking is worse on a short or long wheelbase (long). Others imply the low-air warning may wait until 60 psi exactly.
Rule of thumb
If the pushrod travel at a slack adjuster is beyond the manual's adjustment limit, the brake is out of adjustment and the vehicle cannot be driven until it is fixed.