Alabama CDL General Knowledge common mistakes
Alabama CDL General Knowledge · Understand the traps and how to avoid them.
Answering 'stopping distance' questions using only perception and braking distance, omitting reaction distance from the total.
Candidates memorize the braking-distance formula and forget that total stopping distance is perception distance plus reaction distance plus braking distance.
What to do instead
Practice writing the three-part chain every time: perception distance + reaction distance + braking distance = total stopping distance, and note that reaction distance grows with speed and driver alertness.
Choosing a following distance based on the posted speed limit alone, ignoring vehicle weight, load, and road conditions.
The 'one second per ten feet' rule is easy to memorize, and candidates apply it mechanically without adjusting for heavy loads, slippery roads, or poor visibility.
What to do instead
Memorize the baseline seconds rule, then drill the adjustment factors (add a second for speeds over 40 mph, for bad weather, for heavy loads, and at night) and apply them in scenario questions.
Treating the cargo securement question as satisfied by 'tie it down' rather than stating the required number of tiedowns and aggregate working load.
Candidates skim the cargo rules and miss the specific tiedown counts and strength requirements that appear in answer choices.
What to do instead
Memorize the tiedown count rules by cargo length and weight and the requirement that the securement system's aggregate working load limit exceed the cargo weight; practice matching those numbers to answer choices.
Assuming the air brake system is at operating pressure immediately after start-up and answering pressure-build questions without the required psi-per-minute figure.
Candidates confuse the warning buzzer threshold with the build-up rate and never learn the specific minimum pressure gain per minute for a single or dual system.
What to do instead
Memorize the distinct numbers: warning device activation, spring brake pop-out pressure, governor cut-out, and the minimum build-up rate per minute; practice distinguishing them in multiple-choice stems.
Skipping the air brake leak-down test in inspection questions, or describing only a visual check of the gauges without stating the allowed pressure loss.
The static leak test has multiple steps and specific allowable losses, so candidates summarize it as 'check for leaks' and lose the detail points.
What to do instead
Memorize the leak test sequence and the allowable pressure drop for both applied and released brakes, and practice writing the full procedure in order.
Coupling or uncoupling a combination vehicle in the wrong order, such as releasing the fifth-wheel latch before lowering the landing gear or pulling the tractor away with air lines still connected.
The sequence has many steps and candidates learn it as a list without understanding why each step prevents a specific failure.
What to do instead
Practice the coupling and uncoupling sequences as numbered checklists and attach the hazard to each step (trailer creep, landing gear collapse, air line damage) so order becomes logical rather than rote.
Performing the pre-trip inspection as a quick walk-around and answering inspection questions with 'check it' instead of naming the specific defect and the pass/fail criterion.
Candidates treat inspection as a memory test of parts rather than a procedure with acceptance criteria, so they omit belts, hoses, brake adjustment, and leak checks.
What to do instead
Study the inspection as a fixed route around the vehicle and for each item state what you look for and what makes it a defect; practice reciting the route and criteria aloud.
Answering skid-recovery and emergency-braking questions by describing hard braking and steering away from the skid.
Instinct from passenger-car driving conflicts with the CDL answer, which emphasizes releasing the brakes to regain traction and steering in the direction of the skid.
What to do instead
Drill the counterintuitive rules explicitly: release the brakes to restore wheel roll, steer in the direction the rear is sliding, and avoid hard braking on slippery surfaces.
Shifting on a downgrade or before a curve instead of selecting the right gear before the hazard, and coasting in neutral to save fuel.
Candidates carry over manual-transmission habits from cars and underestimate how much speed builds on a grade before engine braking takes effect.
What to do instead
Memorize the rule to select a gear that holds the load's speed before descending and to downshift before curves; treat coasting in neutral as a distinct violation question.
Treating a railroad-highway crossing as a yield situation and answering that stopping is required only if a train is visible.
Candidates apply general right-of-way intuition and miss the vehicle-specific stopping requirements for buses, hazmat, and other vehicles that must stop at every crossing.
What to do instead
Memorize which vehicles must stop at all crossings regardless of train presence, and practice the look-and-listen procedure and the rule against stopping on the tracks.