CDL General Knowledge Test Sample Questions and Explanations

When a tire fails: hold the steering wheel firmly with both hands and stay off the brake unless you are about to hit something. Once the vehicle slows, brake very gently, pull off the road, and check all the tires.

Wrong choices

• Brake hard right away to stop quickly: Braking after a blowout can make you lose control.
• Steer onto the shoulder at full speed: Quick moves at full speed can cause a rollover or skid.

Stopping is not always the safest choice. You can almost always turn to miss an obstacle more quickly than you can stop. But top-heavy vehicles and multiple trailers may flip over.

Wrong choices

• Stop before reaching the obstacle: A large vehicle needs a long distance to stop.
• Both take the same amount of time: Turning is usually quicker than stopping.

Total stopping distance = perception distance + reaction distance + braking distance. You keep moving while your brain recognizes the hazard and while your foot moves to the brake.

Wrong choices

• Reaction distance, following distance, and braking distance: Following distance is the gap you keep, not part of stopping.
• Braking distance only: You travel a long way before the brakes even start working.

When you double your speed, the impact and the braking distance become about four times greater. Triple the speed and they become about nine times greater.

Wrong choices

• It becomes about twice as long: Braking distance grows much faster than speed.
• It stays about the same: Speed has a big effect on braking distance.

Front tires need at least 4/32 inch of tread depth in every major groove. All other tires need at least 2/32 inch. Front tires need more tread because they steer the vehicle.

Wrong choices

• 2/32 inch in every major groove: 2/32 inch is the minimum for the other tires, not the front tires.
• 1/32 inch in every major groove: This is far too little tread for any tire on a commercial vehicle.

The required emergency equipment is:

1. Spare electrical fuses (unless the vehicle has circuit breakers)
2. Three red reflective warning triangles
3. A properly charged and rated fire extinguisher

Wrong choices

• A spare tire, tire chains, and a flashlight: Chains and tire-changing tools are optional items, not the required set.
• A first-aid kit, a jack, and a road map: These can be useful, but they are not the required emergency equipment.

Back and turn toward the driver's side whenever you can. You can see the rear of your vehicle by looking out the side window. It is worth going around the block to set up a driver-side back.

Wrong choices

• Toward the passenger (right) side: Backing to the right is very dangerous because you cannot see as well.
• Straight back without looking at the mirrors: You should always use the mirrors on both sides.

Use at least one tiedown for each 10 feet of cargo. No matter how small the cargo, use at least two tiedowns.

Wrong choices

• One: One tiedown is never enough, even for small cargo.
• Four: Four may be needed for longer cargo, but the minimum is two.

Inspect the cargo and its securing devices within the first 50 miles of a trip. After that, re-check every 3 hours or 150 miles (whichever comes first) and after every break.

Wrong choices

• Within the first 150 miles: 150 miles is the later re-check interval, not the first check.
• At the end of the day: Cargo must be checked early in the trip.

It is illegal to drive a commercial motor vehicle with a BAC of 0.04% or more. That is half the limit most states use for regular drivers. Any detectable amount below 0.04% still puts you out of service for 24 hours.

Wrong choices

• 0.08%: 0.08% is the general limit for regular drivers, not for CMV drivers.
• 0.10%: This is much higher than the CMV limit.