CCDL Permit Prep

General Knowledge · page 11 of 19

General Knowledge questions 201–220

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. To avoid a trailer jackknife, the MOST important action is:

    • AAvoid locking the trailer brakes; brake only as hard as traction allowsCorrect
    • BSteer sharply to realign the trailer
    • CApply the parking brake first, then the service brakes
    • DAccelerate to straighten the trailer

    Trailer jackknifes are usually caused by locking the trailer wheels under hard braking. Avoiding locked trailer wheels (brake only as hard as the traction allows, or use ABS) is the primary prevention.

    FMCSA CDL Testing System — Emergency Maneuvers · Emergency Maneuvers — Jackknife Prevention · verified 2026-09-08

  2. If your vehicle begins to hydroplane, you should:

    • AApply the brakes firmly to regain traction
    • BIncrease speed to get through the water quickly
    • CSteer sharply toward dry pavement while braking hard
    • DRelease the accelerator and avoid braking until traction returnsCorrect

    During hydroplaning, tires lose contact with the road and braking or steering can cause a skid. Ease off the accelerator gently and avoid braking until the tires regain contact and traction returns.

    FMCSA CDL Testing System — Emergency Maneuvers · Emergency Maneuvers — Hydroplaning · verified 2026-09-08

  3. When an engine fire occurs, you should NOT:

    • APull off the road and stop
    • BTurn off the ignition
    • COpen the hood to fight the fire with an extinguisherCorrect
    • DCall 911 after stopping

    You should NOT open the hood during an engine fire — doing so introduces oxygen and can cause a flash fire or explosion. Use the extinguisher from the side, aiming at the base of the fire through a wheel well or from under the vehicle.

    FMCSA CDL Testing System — Emergency Maneuvers · Emergency Maneuvers — Fire Response · verified 2026-09-08

  4. During a drive-wheel braking skid, the first recovery step is to:

    • ABrake harder so the locked drive wheels regain grip
    • BStop braking so the rear wheels roll again, then counter-steer as neededCorrect
    • CPush in the clutch and keep the brakes applied until the skid stops
    • DApply only the trailer hand brake to pull the rig straight

    To correct a drive-wheel braking skid, stop braking so the rear wheels can roll again, then counter-steer as the vehicle turns back on course so it does not skid the other way. Pushing in the clutch is the fix for a drive-wheel acceleration skid on a very slippery surface, not a step in correcting a braking skid.

    FMCSA Commercial Driver License Manual (as published in the Washington State Commercial Driver Guide) · Sections 2.19.1 Drive-wheel skids and 2.19.2 Correcting a drive-wheel braking skid · verified 2026-09-29

  5. During non-ABS stab braking, when should full braking be applied again after release at wheel lock?

    • APressing the brake pedal to the floor and holding it
    • BAfter the wheels start rolling againCorrect
    • CAlternating between the service and parking brakes
    • DApplying only the trailer brake in an emergency, leaving the tractor's own brakes unused during the emergency

    Wait for rotation before reapplying. Repeated light pumping is not this technique; sustained wheel lock prevents control.

    Oregon DMV Commercial Driver Manual · 2.17.2 · verified 2026-09-07

  6. During a pre-trip inspection, the steering wheel turns freely before the road wheels respond. What should the driver do?

    • AHave the steering system evaluated before operationCorrect
    • BAdd air to the tires and continue
    • CPump the brake pedal to remove the play
    • DDrive slowly and recheck at the next stop

    Free movement before the road wheels respond can indicate worn steering components. Have the steering system evaluated before operation under the vehicle manufacturer specifications and applicable inspection criteria.

    FMCSA-hosted Commercial Driver License Manual · Section 5.1.2 and 5.3.3 — Compressor buildup and final air-brake check · verified 2026-09-07

  7. During the vehicle inspection test, what should you check on a brake chamber?

    • AIt is not leaking, cracked, or dented, and is mounted securelyCorrect
    • BIts spring-brake color matches the axle-housing stamp
    • CIts size stamp matches a number on the axle housing
    • DIt has a fixed number of bolt holes

    The manual's brake inspection says to see that brake chambers are not leaking, cracked, or dented and are mounted securely.

    FMCSA Commercial Driver's License Manual (July 2014) · Section 11.2.3 - Brakes (Brake Chambers) · verified 2026-09-25

  8. For a bus, truck, or truck tractor, what is the minimum tread depth in a major groove for a tire other than a front tire?

    • A3/32 inch
    • B2/32 inchCorrect
    • C4/32 inch
    • D1/4 inch

    49 CFR 393.75(c) requires at least 2/32 inch in a major tread groove on tires other than front tires; front tires have a 4/32-inch minimum.

    49 CFR 393.75 Tires · 393.75(c) · verified 2026-09-25

  9. During an air-brake pre-trip inspection, the engine is off and all brakes are released. For a single vehicle, static air pressure loss must be:

    • ALess than 1 psi per minute
    • BLess than 3 psi per minute
    • CLess than 2 psi per minuteCorrect
    • DLess than 5 psi per minute

    For a single vehicle, static air loss with the engine off and all brakes released must be less than 2 psi in one minute. For a combination vehicle, the limit is less than 3 psi. Applied-brake limits are different.

    FMCSA-hosted Commercial Driver License Manual · Section 5.1.2 and 5.3.3 — Compressor buildup and final air-brake check · verified 2026-09-07

  10. A vehicle's applicable low-air warning threshold is 60 psi. During a secured pre-trip test, the gauge falls to 55 psi with no warning. What should you conclude?

    • AThe warning test passed because the gauge still shows pressure
    • BThe warning device failed its check and must be repaired before drivingCorrect
    • CThe test is valid only after the spring brakes apply
    • DThe compressor must be running before judging the warning

    The stated threshold requires the warning before pressure falls below 60 psi. No warning at 55 psi is a failed check. Keep the vehicle secured and repair the fault before driving; warning thresholds must follow the applicable vehicle requirements.

    FMCSA Commercial Driver License Manual · 5.3.3 — Test Low Pressure Warning Signal · verified 2026-09-07

  11. When checking coupling during a pre-trip on a combination vehicle, what is the 'tug test'?

    • AMoving forward slowly with the trailer brakes applied to check for proper couplingCorrect
    • BTesting the air brake connection by activating the trailer brakes
    • CPulling the air line connections to check they are secure
    • DChecking the kingpin by pushing the landing gear up and down

    A gentle pull against locked trailer brakes checks that the connection resists separation. Secure the tractor and also inspect for no plate gap, jaws around the kingpin shank, and a secured locking mechanism. The tug does not replace those visual checks.

    Oregon DMV Commercial Driver Manual · 6.2.4 Air-lines; 6.2.5 Hose Couplers; 6.4.1 Coupling; 6.4.2 Uncoupling · verified 2026-09-07

  12. Under 49 CFR §393.47(e)(1), how is pushrod stroke limited for the brake actuators listed there?

    • AIt must not exceed the value in the applicable table.Correct
    • BIt may exceed the table value when air pressure is normal.
    • CIt is checked only after the vehicle has been driven.
    • DNo limit applies if the brake pedal feels normal.

    Section 393.47(e)(1) requires pushrod stroke not to exceed the values in the applicable tables. This question does not assign an out-of-service status.

    Electronic Code of Federal Regulations: 49 CFR §393.47 · §393.47(e)(1): Brake adjustment limits · verified 2026-09-27

  13. A driver finds a defect that could affect safe operation and it remains at the end of the day. What must the required DVIR do?

    • AList the vehicle parts and condition and identify the defect, then be signed by the driverCorrect
    • BDescribe only defects already classified as out of service
    • CWait until the annual inspection to record it
    • DReplace the defect description with a no-defect certification

    When a report is required, it must cover the listed vehicle parts and accessories and identify defects or deficiencies that could affect safe operation or cause a breakdown. The driver must sign it. Federal law does not require a no-defect DVIR solely because the workday ended.

    49 CFR § 396.11 · § 396.11(a)(2)(i)–(ii) — Report content and signature · verified 2026-09-19

  14. How often must a CMV receive a full periodic inspection under 49 CFR Part 396?

    • AEvery 30 days
    • BEvery 6 months
    • CEvery 25,000 miles
    • DAt least once every 12 monthsCorrect

    Under 49 CFR 396.17, a commercial motor vehicle subject to the rule must receive a complete periodic inspection at least once every 12 months. The carrier must keep the inspection record as required by the rule.

    eCFR 49 CFR 396.17 — Periodic inspection · 396.17(a) — Periodic inspection · verified 2026-09-07

  15. What should you check on the landing gear of a trailer during a vehicle inspection?

    • AThat it is fully extended to provide maximum ground clearance
    • BThat it is retracted and the crank handle is securedCorrect
    • CThat the landing gear legs are touching the ground for stability
    • DThat it is painted the proper color

    During inspection with the trailer coupled, landing gear must be fully retracted and the crank handle secured so it does not catch on anything during travel.

    FMCSA CDL Testing System — Vehicle Inspection · Vehicle Inspection — Landing Gear · verified 2026-09-08

  16. Under 49 CFR 393.60, which windshield condition does not meet the federal rule unless an exception applies?

    • AAny crack that is not intersected by another crack
    • BA small isolated damaged area within the stated size and spacing exception
    • CDamage in the specified driver-view area that is not a listed exceptionCorrect
    • DTint that meets the rule's luminous-transmittance requirement

    The federal rule requires the specified driver-view area to be free of discoloration or damage, subject to listed exceptions. A crack that is not intersected by another crack and a small isolated damaged area meeting the size and spacing exception are allowed. This question states the federal condition rule; it does not assign an out-of-service classification.

    eCFR 49 CFR 393.60 — Glazing in specified openings · 393.60(c) — Windshield condition and exceptions · verified 2026-09-07

  17. Under the federal Interstate Highway System limits, what maximum weight generally applies to a single axle?

    • A12,000 lbs
    • B20,000 lbsCorrect
    • C34,000 lbs
    • D40,000 lbs

    Federal Interstate Highway System limits generally set a 20,000-pound single-axle limit. State rules, permits, axle spacing, and other exceptions can change what applies on a specific route.

    23 U.S.C. § 127 · Weight — Axle Limits · verified 2026-06-30

  18. If you move a load forward in a trailer, what effect does this have on axle weights?

    • AIt increases the rear axle weight and decreases the front axle weight
    • BIt has no effect on axle weight distribution
    • CIt decreases trailer-axle weight and increases load on the tractor's drive axlesCorrect
    • DIt only affects the trailer axle weight

    Moving cargo forward shifts load toward the tractor, increasing load on the drive axles and reducing load on the trailer axles. Weight distribution affects braking, steering, and legal compliance.

    FMCSA CDL Testing System — Weight · Weight Distribution — Shifting Loads · verified 2026-06-30

  19. The Federal Bridge Formula is used to determine:

    • AThe maximum speed allowed on bridges
    • BThe permit fee for overweight loads
    • CThe minimum number of axles required for heavy loads
    • DThe maximum weight allowed based on the number and spacing of axlesCorrect

    The Federal Bridge Formula (also called Bridge Formula B) calculates the maximum legal weight based on the number of axles and the distance between the outer axles of any group, to protect bridge structures.

    23 U.S.C. § 127 · Weight — Bridge Formula · verified 2026-06-30

  20. What is 'gross combination weight rating' (GCWR)?

    • AThe greater of the displayed manufacturer rating or the applicable combined rated or actual weightsCorrect
    • BThe total weight of cargo only
    • CThe combined weight of the truck and its fuel
    • DThe federally mandated maximum weight for all trucks

    Under 49 CFR 383.5, GCWR is the greater of a displayed manufacturer value for the power unit or the applicable sum of the power unit and towed-unit GVWRs or actual gross weights that produces the highest value.

    49 CFR § 383.5 · Definitions — Gross combination weight rating · verified 2026-09-09