CCDL Permit Prep

General Knowledge · page 1 of 19

General Knowledge questions 1–20

Part of the 376-question General Knowledge pool. Each answer cites the FMCSA CDL Manual or the federal rule it comes from.

Practise these as a timed set

  1. At what blood alcohol concentration does the federal CDL disqualification threshold begin for a driver operating a commercial motor vehicle that requires a CDL?

    • A0.04%Correct
    • B0.08%
    • C0.02%
    • D0.00%

    The federal CDL disqualification threshold begins at 0.04% BAC when operating a commercial motor vehicle that requires a CDL. This is not permission to drive with a lower BAC. Separate on-duty alcohol prohibitions apply. Do not confuse the disqualification threshold with an amount that is safe or allowed before driving.

    49 CFR § 383.51 · Table 1, item (3): alcohol concentration of 0.04 or greater while operating a CMV · verified 2026-09-08

  2. When should you downshift to control speed on a long downgrade?

    • AAfter gaining too much speed
    • BBefore starting down the hillCorrect
    • CHalfway down the hill
    • DAt the bottom of the hill

    Select a lower gear before starting down a long downgrade to use engine braking effectively and preserve your service brakes.

    FMCSA Commercial Driver's License Manual · Section 2.16 — Mountain Driving: select a lower gear before starting down a long downgrade · verified 2026-09-08

  3. What is the minimum tread depth in a major groove for a front tire on a bus, truck, or truck tractor?

    • A2/32 inch
    • B4/32 inchCorrect
    • C6/32 inch
    • D8/32 inch

    Federal rules require at least 4/32 inch tread depth in a major groove on the front tires of a bus, truck, or truck tractor. Other tires need at least 2/32 inch. This is a federal operating minimum; a state, carrier, or vehicle rule may be stricter.

    eCFR 49 CFR 393.75 — Tires · 393.75(b) — Tread groove depth · verified 2026-09-07

  4. The purpose of a pre-trip inspection is to:

    • AIdentify problems that could cause a crash or breakdownCorrect
    • BDocument mileage for the trip log
    • CSatisfy DOT requirements only
    • DCheck fuel levels

    Before driving, the driver must be satisfied that the vehicle is in safe operating condition. Inspecting equipment helps find defects before they cause a crash or breakdown; it is more than a fuel check or paperwork task.

    49 CFR § 396.13 · 396.13(a) safe operating condition before driving · verified 2026-09-07

  5. According to the CDL manual, how often should you check your mirrors while driving?

    • ARegularly, and more often in special situationsCorrect
    • BOnly when changing lanes
    • COnly when backing up
    • DOnce at the start of each trip

    The manual says to check your mirrors regularly and more often in special situations, to know where other vehicles are and whether they move into your blind spots.

    FMCSA Commercial Driver License Manual (July 2014) · Section 2.4.2: Seeing to the Sides and Rear · verified 2026-09-25

  6. If your commercial vehicle is hydroplaning, you should:

    • ABrake firmly to slow down before the tires lose more grip
    • BAccelerate gently so the drive tires cut through the water
    • CRelease the accelerator, avoid braking, and keep the wheel straightCorrect
    • DSteer sharply toward the shoulder to find a drier surface

    When hydroplaning, release the accelerator and push in the clutch if it is safe; do not use the brakes, and keep the steering wheel straight until traction returns.

    FMCSA Commercial Driver License Manual · Section 2.6.2: Hydroplaning · verified 2026-09-29

  7. At speeds below 40 mph, what minimum following-distance rule applies to a commercial vehicle?

    • AAt least one second per 10 feet of vehicle lengthCorrect
    • B2 seconds, regardless of the vehicle's length
    • C4 seconds
    • D10 seconds

    Follow the formula: one second for each 10 feet of vehicle length at speeds below 40 mph, plus one extra second above 40 mph.

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely — Following Distance · verified 2026-09-08

  8. Before driving a commercial motor vehicle, what must the driver be satisfied about the cargo?

    • AIt is properly distributed and adequately securedCorrect
    • BIt is covered by a radio dispatch notice
    • CIt is visible to the driver in every mirror
    • DIt includes an extra set of tie-downs

    Federal rules require the driver to be satisfied that cargo is properly distributed and adequately secured before driving a commercial motor vehicle.

    49 CFR § 392.9 · Section 392.9(a): cargo properly distributed and adequately secured · verified 2026-09-08

  9. What can result from too much weight on the steering axle?

    • ABetter steering
    • BHard steering and damage to steering axleCorrect
    • CImproved fuel economy
    • DSmoother ride

    Too much weight on the steering axle makes steering difficult and can damage the steering axle.

    FMCSA Commercial Driver License Manual · Section 3: Transporting Cargo Safely · verified 2026-09-08

  10. You are driving a 40-foot vehicle at 35 mph. What is the minimum following distance you should maintain?

    • A2 seconds
    • B3 seconds
    • C4 secondsCorrect
    • D5 seconds

    At speeds below 40 mph, use one second for each 10 feet of vehicle length. A 40-foot vehicle requires at least 4 seconds.

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely - Space Management · verified 2026-09-08

  11. Under the FMCSA manual's basic model, before adding air-brake lag, which three distances make up stopping distance?

    • APerception distance, reaction distance, braking distanceCorrect
    • BSpeed, weight, road conditions
    • CEye lead time, following distance, space cushion
    • DTire tread, brake condition, vehicle weight

    The basic model adds perception, reaction, and braking distance. For air-brake vehicles, the manual adds brake-lag distance as a fourth component.

    FMCSA Commercial Driver's License Manual (July 2014 edition) · Sections 2.6.1 and 5.4.4: basic stopping-distance model and added air-brake lag · verified 2026-09-20

  12. If your CMV stops on the shoulder of a divided or one-way highway, where should you place warning devices?

    • A10 feet, 50 feet, and 100 feet behind the vehicle
    • BOne within 10 feet of the rear, plus others at 100 and 200 feet toward approaching trafficCorrect
    • C50 feet, 100 feet, and 200 feet behind the vehicle
    • D100 feet, 200 feet, and 300 feet behind the vehicle

    On a divided or one-way highway, place one warning device at the traffic side within 10 feet of the rear. Place the other two at 100 and 200 feet toward approaching traffic in the lane or shoulder your vehicle occupies.

    49 CFR § 392.22 · § 392.22(b)(2)(v) — Divided or one-way highway placement · verified 2026-09-19

  13. According to federal regulations, you must inspect your cargo within the first ____ miles of your trip.

    • A75 miles
    • B50 milesCorrect
    • C25 miles
    • D100 miles

    Federal rules require cargo securement devices to be reexamined within the first 50 miles. They must then be reexamined and adjusted as needed after 3 hours of driving or 150 miles, whichever occurs first, and after a change of duty status.

    49 CFR § 392.9 · Section 392.9(b): reexamination of cargo securement devices · verified 2026-09-08

  14. What does the federal bridge formula allow when a vehicle's axle groups are spaced farther apart?

    • AOnly applies to bridges over water
    • BPermits heavier loads on trucks with axles closer together
    • CIs the same for all states
    • DPermits heavier loads on trucks with axles farther apartCorrect

    The bridge formula permits heavier weights when axles are spaced farther apart to distribute weight over more road surface.

    FMCSA Commercial Driver License Manual · Section 3: Transporting Cargo Safely - Weight and Balance · verified 2026-09-08

  15. Name two situations where you should downshift:

    • ABefore starting down a hill and before entering a curveCorrect
    • BWhile going up a hill and while on straight roads
    • CAfter stopping and after making a turn
    • DWhile accelerating and while hydroplaning

    Downshift before starting down a hill (for engine braking) and before entering a curve (for better control).

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely - Shifting Gears · verified 2026-09-08

  16. Retarders help slow the vehicle, but they:

    • AShould always be used in wet weather
    • BCan cause the drive wheels to skid when traction is poorCorrect
    • CIncrease fuel consumption
    • DAre only effective at high speeds

    Retarders can cause drive wheels to skid when traction is reduced (wet, icy, or snowy conditions). Turn them off in poor conditions.

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely - Retarders · verified 2026-09-08

  17. What is the proper way to make a right turn in a commercial vehicle?

    • ATurn wide before the turn
    • BStay tight to the curb throughout
    • CTurn wide as you complete the turnCorrect
    • DSpeed up through the turn

    Keep your rear wheels close to the curb during initial turn, then complete the turn by swinging wide to accommodate off-tracking.

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely - Turns · verified 2026-09-08

  18. You are driving a 50-foot truck at 50 mph. The safe following distance is at least:

    • A6 secondsCorrect
    • B5 seconds
    • C7 seconds
    • D8 seconds

    At 50 mph (above 40), add 1 second to base formula: 5 seconds for 50 feet + 1 second for speed = 6 seconds minimum.

    FMCSA Commercial Driver License Manual · Section 2: Driving Safely - Space Management · verified 2026-09-08

  19. During a pre-trip, you find a vehicle condition likely to cause an accident or breakdown. What should you do?

    • ADrive carefully to a repair shop
    • BDo not drive until it is repairedCorrect
    • CReport it but continue driving
    • DComplete your route first

    A motor vehicle must not be operated in a condition likely to cause an accident or breakdown. The rule has a narrow exception for an unsafe condition discovered while operating on a highway, which does not make a pre-trip departure safe.

    eCFR 49 CFR 396.7 · 49 CFR 396.7(a): unsafe operations forbidden · verified 2026-09-08

  20. If you have a tire failure while driving, you should:

    • AApply the service brakes hard immediately to stop
    • BHold the wheel firmly, stay off the brakes, let it slowCorrect
    • CTurn the steering wheel sharply toward the shoulder
    • DSpeed up briefly to maintain control of the vehicle

    Stay off the brakes and accelerator, hold the steering wheel firmly, and let the vehicle slow down on its own before braking gently.

    FMCSA Commercial Driver License Manual · Section 2: Emergencies · verified 2026-09-08