Kansas CDL Combination cheat sheet

A combination vehicle must be checked for coupling security before every trip: tug test (pull gently against the trailer with the trailer brakes set), visual check of the fifth-wheel jaws closed under the kingpin, and a pull test with the tractor parking brake applied.

Air brake systems on a combination unit must be inspected for low-air warning (buzzer/light by 60 psi), governor cut-in/cut-out, static leak rate (no more than 3 psi per minute with engine off and brakes released; 4 psi per minute with brakes applied), and tractor protection valve function.

Trailer hand valve (spike) is used only to test trailer brakes, never as a parking brake. Pulling it while driving can cause a jackknife because only the trailer brakes apply.

The tractor protection valve closes and prevents air loss if a trailer breaks away or a coupler fails; the trailer emergency spring brakes then set automatically when air pressure drops below about 45 psi.

Required following distance for a combination vehicle is one second per 10 feet of vehicle length at speeds below 40 mph, plus one extra second; above 40 mph add one additional second. A 60-foot rig at 55 mph needs at least 7 seconds.

Off-tracking: the rear wheels of a tractor-trailer follow a shorter path than the front wheels. The longer the wheelbase and the sharper the turn, the greater the off-track; swing-out at the front of the trailer occurs in the opposite direction.

Before backing, get out and check behind the trailer; use a helper if possible. Back toward the driver's side (left) whenever possible, and correct drift with small steering movements because large corrections amplify trailer angle.

Total stopping distance equals perception distance + reaction distance + brake lag distance + effective braking distance. At 55 mph a loaded combination needs roughly 300+ feet on dry pavement; wet or icy surfaces multiply this substantially.

When uncoupling, set the trailer parking brakes, lower the landing gear to firm ground, disconnect glad hands and electrical cord, then pull the tractor forward slightly to release the fifth-wheel jaw before pulling clear.

The CDL skills test has three parts: pre-trip vehicle inspection, basic vehicle control (including straight-line backing, offset backing, and alley docking), and on-road driving. All three must be passed.

During the pre-trip inspection, the candidate must verbally identify each component, state what is being checked, and describe what a defect would look like; missing a critical item such as brakes or coupling devices is an automatic failure.

For the coupling/uncoupling portion, the candidate must demonstrate proper sequence: chock wheels, align tractor and trailer, back under the kingpin, tug test, connect air lines, raise landing gear, and verify fifth-wheel jaws are locked.

For straight-line backing, the candidate may use mirrors and may pull forward once to correct; crossing a boundary line or hitting a cone is a point deduction. Excessive pull-ups or going out of bounds fails the maneuver.

For offset backing (right or left), the candidate must move the trailer into an adjacent lane while staying within boundaries; the maneuver is scored on setup, control, and final position.

For alley docking, the candidate must back into a simulated dock area and stop with the rear of the trailer within the marked space; the vehicle must be straight and within the lines, and the candidate must not strike the barrier.

On-road driving evaluates lane control, mirror use, signaling, speed management, gear selection (including proper use of the range and splitter for a manual transmission), and railroad crossing and bridge clearance procedures.

Automatic failure items during the skills test include: hitting a cone or boundary, causing an accident, failing to yield, running a red light or stop sign, and any dangerous action requiring the examiner to intervene.

The examiner scores the pre-trip inspection on a point system; the candidate must correctly identify all critical items, and any unlisted critical defect (brakes, steering, coupling) fails the inspection portion.