CCDL Permit Prep

General Knowledge · page 7 of 19

General Knowledge questions 121–140

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. Reaction distance is the distance your vehicle travels:

    • ABefore you see the hazard while the vehicle is still moving
    • BAfter you see a hazard and before you physically hit the brakesCorrect
    • CAfter the brakes are fully applied
    • DWhile checking your mirrors

    FMCSA Section 2.6.1 defines reaction distance as the distance traveled, in ideal conditions, before you physically hit the brakes in response to a hazard seen ahead. It is different from perception distance and braking distance.

    FMCSA Commercial Driver's License Manual (2005 CDL Testing System) · Section 2.6.1: Stopping Distance · verified 2026-09-08

  2. When you double your speed from 20 to 40 mph, your braking distance increases by about:

    • ATwo times
    • BIt stays the same
    • CThree times
    • DFour timesCorrect

    Braking distance grows with the square of speed, so doubling your speed roughly quadruples the distance needed to stop.

    FMCSA Commercial Driver's License Manual · Section 2.6 - Stopping Distance · verified 2026-09-08

  3. Compared with a fully loaded truck, an empty truck generally:

    • AHas the same stopping distance
    • BCannot use its brakes at highway speed
    • CStops in a much shorter distance
    • DNeeds a longer stopping distance because it has less tractionCorrect

    An empty truck has less weight pressing the tires down, so they grip less and the brakes can lock, lengthening the stop.

    FMCSA Commercial Driver's License Manual · Section 2.7 - Matching Speed To Traction · verified 2026-09-08

  4. In the FMCSA manual's air-brake example, at 55 mph on dry pavement, total stopping distance is:

    • AOver 450 feetCorrect
    • B100 feet
    • C300 feet
    • D200 feet

    The manual says air-brake lag adds about 32 feet at 55 mph. Under good traction and brake conditions, total stopping distance is over 450 feet. Actual distance varies.

    FMCSA Commercial Driver's License Manual (July 2014 edition) · Section 5.4.4: air-brake lag and total stopping distance · verified 2026-09-20

  5. If you are placed under an out-of-service order, you may:

    • ANot operate the CMV until the order's conditions are metCorrect
    • BDrive to the nearest truck stop only
    • CContinue if the load is perishable
    • DDrive at reduced speed

    An out-of-service order means you must not operate the CMV until the order is lifted and its conditions are met.

    49 CFR § 383.51 · Disqualification - out-of-service order · verified 2026-09-08

  6. Driving 15 mph or more over the speed limit in a CMV is classified as:

    • AA minor equipment issue
    • BAn out-of-service condition
    • CA parking violation
    • DA serious traffic violationCorrect

    Excessive speeding of 15 mph or more over the limit is a serious traffic violation; two within three years bring a disqualification.

    49 CFR § 383.51 · Serious traffic violations · verified 2026-09-08

  7. You must use your headlights:

    • AOn the highway
    • BWhen other vehicles are present
    • COn unlit roads
    • DFrom dusk to dawn and whenever visibility is lowCorrect

    Headlights are required from dusk to dawn and any time visibility drops, so other drivers can see you and you can see the road.

    FMCSA Commercial Driver's License Manual · Section 2.11 - Driving At Night · verified 2026-09-08

  8. When you intend to turn, you should signal:

    • AJust as you begin the turn
    • BEarly and continuously until the turn is completeCorrect
    • COnly if other vehicles are nearby
    • DOnce, briefly, then cancel it before you start turning

    Signaling early and keeping it on until you finish the turn gives other drivers time to react to a slow-moving large vehicle.

    FMCSA Commercial Driver's License Manual · Section 2.2 - Communicating - Signaling · verified 2026-09-29

  9. A safe rule for following distance under 40 mph is at least:

    • A2 seconds total regardless of length
    • B1 second for the whole vehicle
    • C1 second for every 10 feet of vehicle lengthCorrect
    • DHalf a second per axle

    Below 40 mph, allow one second of following distance for each 10 feet of vehicle length, then add a second above 40 mph.

    FMCSA Commercial Driver's License Manual · Section 2.7 - Speed And Distance Ahead · verified 2026-09-08

  10. The most important reason to do a vehicle inspection is:

    • ATo satisfy your dispatcher
    • BTo pass the time before a trip
    • CTo improve fuel economy
    • DSafety for yourself and other road usersCorrect

    Inspections find problems that could cause a breakdown or crash, protecting the driver and everyone sharing the road.

    FMCSA Commercial Driver's License Manual · Section 2.1 - Vehicle Inspection Overview · verified 2026-09-08

  11. A first conviction for driving a CMV while using a controlled substance results in disqualification for at least:

    • AOne yearCorrect
    • B60 days
    • C30 days
    • D10 days

    A first conviction for a major controlled-substance offense while operating a CMV results in disqualification for at least one year.

    49 CFR § 383.51 · Disqualification - alcohol and controlled substances · verified 2026-09-08

  12. When approaching a railroad crossing without a gate or signal, you should:

    • ASpeed up to clear it quickly
    • BSlow down, check both directions, and be ready to stopCorrect
    • CStop on the tracks to look
    • DSound your horn and proceed without slowing

    Always slow and look both ways at a passive crossing, because a large vehicle takes time to clear the tracks safely.

    FMCSA Commercial Driver's License Manual · Section 2.13 - Railroad Crossings · verified 2026-09-08

  13. Any CDL driver who discovers a hazardous materials leak should:

    • AWash it away with water immediately
    • BKeep people away, stay upwind, and avoid contactCorrect
    • CTouch the material to identify it
    • DContinue driving to the destination

    Without proper training and equipment, keep clear, stay upwind, warn others, and call for trained responders to handle the leak.

    FMCSA Commercial Driver's License Manual · Section 2.18 - Hazardous Materials Awareness · verified 2026-09-08

  14. Which is a warning sign that fatigue is affecting your driving?

    • AFeel completely alert
    • BTurn up the radio
    • CDrink coffee to try to stay alert
    • DBegin to feel drowsy, miss exits, or drift in your laneCorrect

    Drowsiness, missed exits, and lane drifting are warning signs that fatigue is affecting driving. Stop and rest rather than continuing while impaired.

    FMCSA Commercial Driver's License Manual · Section 2.5 - Controlling Speed - Hazard Lights · verified 2026-09-08

  15. When driving a commercial vehicle, you should look ahead a distance equal to about:

    • A2 to 5 seconds of travel
    • BOnly as far as your headlights
    • C30 seconds of travel
    • D12 to 15 seconds of travelCorrect

    Looking 12 to 15 seconds ahead lets you spot hazards early and react smoothly instead of making sudden, dangerous moves.

    FMCSA Commercial Driver's License Manual · Section 2.8 - Seeing - Looking Ahead · verified 2026-09-08

  16. When a vehicle is following you too closely, the best response is to:

    • ASpeed up until the vehicle falls back
    • BBrake hard to warn the following driver
    • CIncrease your following distance from the vehicle ahead and avoid sudden movesCorrect
    • DTurn on your high beams to signal them

    Opening more space ahead lets you brake gently and gives the tailgater more room, lowering the chance of a rear-end crash.

    FMCSA Commercial Driver's License Manual · Section 2.9 - Managing Space - Behind · verified 2026-09-08

  17. If your commercial vehicle begins to hydroplane, you should:

    • ASteer sharply toward the shoulder to try to regain traction
    • BApply the service brakes hard immediately to slow down
    • CRelease the accelerator (and, in a manual transmission, push in the clutch); keep the wheel steadyCorrect
    • DAccelerate steadily to try to regain control of the vehicle

    Release the accelerator and avoid braking while the tires regain contact. In a manual-transmission vehicle, pushing in the clutch lets the drive wheels turn freely; keep the wheel steady.

    FMCSA Commercial Driver's License Manual · Section 2.16 - Hydroplaning · verified 2026-09-08

  18. Roads are usually most slippery:

    • AAfter it has rained for several hours
    • BOnly in freezing weather
    • COnly when fully flooded
    • DJust as rain begins, when water mixes with oilCorrect

    When rain first starts, it lifts oil and dust into a slick film, making the road most slippery before the rain washes it away.

    FMCSA Commercial Driver's License Manual · Section 2.16 - Wet Roads · verified 2026-09-08

  19. When driving through a highway work zone in a CMV, you should:

    • AChange lanes frequently to keep moving
    • BSlow down, increase following distance, and watch for workers and sudden stopsCorrect
    • CMaintain your normal highway speed
    • DTailgate the vehicle ahead to keep the lane moving

    Work zones have narrowed lanes, workers, and abrupt slowdowns, so reduced speed and extra space let a heavy vehicle stop in time.

    FMCSA Commercial Driver's License Manual · Section 2.10 - Seeing Hazards - Work Zones · verified 2026-09-08

  20. Escape ramps on steep downgrades are designed to:

    • AProvide a rest area for tired drivers
    • BStore snow removal equipment
    • CLet trucks pass slower vehicles
    • DStop a runaway vehicle using soft gravel or an upgradeCorrect

    An escape ramp uses deep loose gravel or an upgrade to safely stop a vehicle whose brakes have failed on a long downgrade.

    FMCSA Commercial Driver's License Manual · Section 2.14 - Mountain Driving - Escape Ramps · verified 2026-09-08