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Hazards, weather and emergencies

Selected knowledge practice, not a complete licensing course or practical training.

Hazards, weather and emergencies

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Question 1 of 64
  1. 1. You enter a highway work zone where the lane narrows and the pavement becomes uneven. What should guide your speed?
  2. 2. Why is dropping the wheels of a tall truck onto a low shoulder especially dangerous near roadside signs?
  3. 3. A box is lying in your truck's lane. You cannot tell what is inside. What is the safest assumption?
  4. 4. While approaching a stopped transit bus, which hidden hazard should a truck driver anticipate?
  5. 5. A parked car's reverse lights come on as your truck approaches. What should you prepare for?
  6. 6. A delivery van is stopped beside the road with its rear doors open. What deserves extra attention as you approach?
  7. 7. An exit ramp curves sharply just after beginning downhill. Why should a truck driver assess it before entering?
  8. 8. You notice a car ahead braking unpredictably near an exit. What is the main benefit of treating it as a developing hazard?
  9. 9. When should you enter a delivery destination and set up the navigation display?
  10. 10. A hands-free conversation leaves both hands available. Does that mean it cannot distract a CMV driver?
  11. 11. Under the federal CMV texting rule, may a driver type a routine dispatch reply while stopped at a red light with the engine running?
  12. 12. Which stop is outside the driving definition in the federal CMV texting rule?
  13. 13. A carrier tells a driver to answer routine texts while driving a CMV. How does the federal texting rule apply to the carrier?
  14. 14. Which communication fits the federal exception to the handheld-phone restriction while driving a CMV?
  15. 15. Another driver makes an angry gesture and tries to provoke you. What is the safest response?
  16. 16. A nearby car drifts within its lane while its driver repeatedly looks down. What should you do?
  17. 17. Your eyelids feel heavy and your truck has drifted toward the lane edge twice. What should you do?
  18. 18. A driver cannot recall the last several miles and has missed an exit. What is the safest interpretation?
  19. 19. A tired driver feels more awake after coffee and cold air from a window. What should the driver understand?
  20. 20. Why should a driver avoid darkly tinted glasses when driving at night?
  21. 21. Headlight glare seems worse through a windshield with an oily film inside. What should you do before another night trip?
  22. 22. How should interior cab lighting be managed during night driving?
  23. 23. A truck's headlamps are dirty and one is poorly aimed. What is the right response before driving at night?
  24. 24. Oncoming high beams make it hard to see. Where should you direct your attention?
  25. 25. Which headlight setting generally gives better visibility in fog?
  26. 26. Why is following the vehicle ahead's taillights an unreliable way to navigate dense fog?
  27. 27. Before entering a stretch of very dense fog, you can safely reach a truck stop. What is the safer option if visibility is inadequate?
  28. 28. Which preparation helps keep the windshield usable in freezing conditions?
  29. 29. Snow and ice cover a truck's steps and handholds. What should happen before using them?
  30. 30. After a long drive on a hot day, tire pressure is above its cold reading. Should you bleed air merely to restore the cold reading?
  31. 31. The engine overheats and the cooling system is still hot. What should you do about a pressurized radiator or coolant cap?
  32. 32. Why must a driver monitor engine temperature when using a winter front or radiator cover?
  33. 33. A railroad crossing has a crossbuck but no active lights or gates. What does the lack of active warnings mean?
  34. 34. No train horn is audible as you approach a crossing. What can you safely conclude?
  35. 35. Railroad red warning lights begin flashing while the gate is still upright. What should you do?
  36. 36. One train has just cleared a crossing with several tracks. What must you check before proceeding?
  37. 37. A bus is carrying passengers and is subject to 49 CFR 392.10 at a crossing with no applicable exception. Where must it stop relative to the tracks?
  38. 38. For a vehicle required to stop under 49 CFR 392.10, how should the driver select a gear for crossing railroad tracks?
  39. 39. Traffic is queued just beyond a railroad crossing, leaving room for your cab but not your full combination. What should you do?
  40. 40. Your vehicle is stuck at a crossing and everyone is safely away from the tracks. What information on the blue-and-white ENS sign helps you alert the railroad?
  41. 41. Before a long mountain descent, which combination should determine a truck's safe speed?
  42. 42. During a descent, repeated heavy service-brake use leads to less slowing despite more pedal pressure. What is a likely danger?
  43. 43. Why can poorly adjusted brakes make overheating more likely on a downgrade?
  44. 44. In the handbook's downgrade example, a suitable low gear is selected and the safe speed is 40 mph. When applying the described snub-braking method, at about what speed are the brakes released?
  45. 45. Your truck is gaining speed on a steep descent because its brakes have failed. An escape ramp is ahead. What should guide your decision?
  46. 46. A driver says a heavily loaded truck can always descend a hill in the same gear it used to climb. Is that a reliable rule for modern trucks?
  47. 47. A driver steers around an obstacle with enough room to avoid it. Why should the driver avoid turning the wheel much farther than necessary?
  48. 48. You have safely steered onto a clear shoulder to avoid a collision, and there is room to stop. What is generally safer than immediately jerking back onto the road?
  49. 49. A truck with hydraulic brakes loses pedal pressure. Which temporary response does the handbook describe as sometimes rebuilding enough pressure to help stop?
  50. 50. A front tire blows out, but no immediate collision requires emergency braking. What should you do first?
  51. 51. You hear a tire burst but the truck still seems to handle normally. What should happen after you reach a safe stopping place?
  52. 52. What is the main benefit of functioning ABS during hard braking?
  53. 53. An ABS warning lamp remains on after its normal self-check or comes on while driving. What does that suggest?
  54. 54. A tractor has functioning ABS but its trailer does not. Is the tractor's ABS still useful?
  55. 55. In a straight-line emergency stop with properly functioning ABS on all axles, how should the driver generally use the service brake?
  56. 56. A truck's front tires have lost grip and it continues straight despite steering input. Will turning the wheel much farther solve the skid?
  57. 57. Why can locked tractor drive wheels during braking develop into a jackknife?
  58. 58. You stop to help at a crash and can choose a safe place to park. Why should you stay clear of the immediate crash area?
  59. 59. Smoke indicates a truck fire and the vehicle can still be stopped safely. Which location is preferable?
  60. 60. After stopping safely for an engine fire, what should you avoid?
  61. 61. Smoke is coming from inside a closed box trailer. Why should the driver keep the cargo doors shut?
  62. 62. You do not know what is burning in a load that may contain hazardous materials or which extinguisher is suitable. What should you do?
  63. 63. A trained person has judged a small fire safe to tackle with a suitable extinguisher and a clear escape route. Where should the discharge be aimed?
  64. 64. Visible flames and smoke have stopped after a vehicle fire. What should a driver remember?
Review all 64 questions with answers

  1. You enter a highway work zone where the lane narrows and the pavement becomes uneven. What should guide your speed?

    Correct answer: Leave time and room for workers, equipment and sudden path changes.

    Work zones can combine uneven surfaces, narrow lanes, sharp turns and people near traffic. Reduce speed as needed and actively watch for changing hazards rather than assuming the normal road layout continues.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.2 Hazardous Roads; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  2. Why is dropping the wheels of a tall truck onto a low shoulder especially dangerous near roadside signs?

    Correct answer: The truck may lean toward a sign or another overhead obstacle.

    An edge drop-off can tilt the vehicle. The top of a tall truck may move toward a sign, branch or other obstacle even when the tires miss it. Keep the whole vehicle's clearance in mind.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.2 Hazardous Roads; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  3. A box is lying in your truck's lane. You cannot tell what is inside. What is the safest assumption?

    Correct answer: It may contain a heavy object capable of damaging the vehicle.

    Do not treat an unknown box as harmless. Debris can damage tires, wheels and other parts, including lines beneath a vehicle. Look for a safe response without a sudden unplanned swerve.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.2 Hazardous Roads; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  4. While approaching a stopped transit bus, which hidden hazard should a truck driver anticipate?

    Correct answer: A person stepping into the road from in front of the bus.

    A large stopped vehicle can hide people who enter the road. Slow and remain prepared for a pedestrian to appear; do not assume that leaving a bus means a person has seen your truck.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.3 Drivers Who Are Hazards; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  5. A parked car's reverse lights come on as your truck approaches. What should you prepare for?

    Correct answer: The car may back into your path.

    Lights, moving front wheels and other visible activity can warn that a parked vehicle may enter your path. Treat them as a reason to prepare, not as proof that its driver has seen you.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.3 Drivers Who Are Hazards; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  6. A delivery van is stopped beside the road with its rear doors open. What deserves extra attention as you approach?

    Correct answer: A delivery worker stepping out from a hidden position.

    Delivery activity can put people close to moving traffic, sometimes hidden by the vehicle or its doors. Scan for people and leave space instead of assuming the area beside the van is empty.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.3 Drivers Who Are Hazards; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  7. An exit ramp curves sharply just after beginning downhill. Why should a truck driver assess it before entering?

    Correct answer: The downhill section can build speed before the sharp curve.

    A downgrade can increase speed on the approach to a ramp curve. Plan a suitable entry speed early; waiting until the curve leaves less room to control a heavy vehicle safely.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.2 Hazardous Roads; printed page 2-19, physical PDF page 51; reviewed September 21, 2026. ↗

  8. You notice a car ahead braking unpredictably near an exit. What is the main benefit of treating it as a developing hazard?

    Correct answer: You can plan space and an escape option before an emergency.

    Hazard recognition gives you time to plan. Consider what might happen and how to respond while keeping your observations current; a prediction is not a guarantee of the other driver's movement.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.8.4 Always Have a Plan; printed page 2-21, physical PDF page 53; reviewed September 21, 2026. ↗

  9. When should you enter a delivery destination and set up the navigation display?

    Correct answer: Before driving, while safely parked.

    Set up navigation and other cab controls before starting. If a later change requires attention that should be on driving, find a safe parking place before making it.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.9.7 Don't Drive Distracted; printed page 2-25, physical PDF page 57; reviewed September 21, 2026. ↗

  10. A hands-free conversation leaves both hands available. Does that mean it cannot distract a CMV driver?

    Correct answer: No. It can still take attention away from driving.

    Distraction can be mental as well as physical. A hands-free arrangement does not guarantee full attention to driving, particularly during a demanding conversation or traffic situation.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.9.5 Cell/Mobile Phones / hands-free distraction; printed page 2-24, physical PDF page 56; reviewed September 21, 2026. ↗

  11. Under the federal CMV texting rule, may a driver type a routine dispatch reply while stopped at a red light with the engine running?

    Correct answer: No. A temporary traffic stop still counts as driving.

    49 CFR 392.80 includes temporary traffic stops in its driving definition when the motor is running. A routine work message is not the emergency-communication exception.

    Source: 49 CFR 392.80(a), (c) and (d); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  12. Which stop is outside the driving definition in the federal CMV texting rule?

    Correct answer: Moving off the highway and halting where it is safe to remain.

    The rule distinguishes a temporary traffic delay from moving to the side of or off the highway and halting where the vehicle can safely remain. Choose a genuinely safe location rather than stopping in a travel lane to text.

    Source: 49 CFR 392.80(c); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  13. A carrier tells a driver to answer routine texts while driving a CMV. How does the federal texting rule apply to the carrier?

    Correct answer: The carrier must not allow or require texting while driving.

    49 CFR 392.80 prohibits a motor carrier from allowing or requiring a driver to text while driving. Dispatch needs must be handled without directing the driver to violate that rule.

    Source: 49 CFR 392.80(b); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  14. Which communication fits the federal exception to the handheld-phone restriction while driving a CMV?

    Correct answer: Necessary communication with emergency services about an emergency.

    The exception is for communication necessary with law enforcement or emergency services. Routine business and personal calls do not qualify; this does not make a distracting or unsafe call a good driving choice.

    Source: 49 CFR 392.82(a)-(c); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  15. Another driver makes an angry gesture and tries to provoke you. What is the safest response?

    Correct answer: Avoid engaging and give the driver room to move away.

    Do not turn another person's aggressive behavior into a confrontation. Keep your attention on safe driving, avoid retaliation and allow separation when you can do so safely.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.10.3 Confrontation with an Aggressive Driver; printed page 2-26, physical PDF page 58; reviewed September 21, 2026. ↗

  16. A nearby car drifts within its lane while its driver repeatedly looks down. What should you do?

    Correct answer: Allow extra room and be ready for an unexpected movement.

    Drifting and diverted attention can indicate distraction. Increase your margin for an unpredictable movement rather than relying on the other driver to notice you or signal reliably.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.9.8 Other Distracted Drivers; printed page 2-25, physical PDF page 57; reviewed September 21, 2026. ↗

  17. Your eyelids feel heavy and your truck has drifted toward the lane edge twice. What should you do?

    Correct answer: Stop at the nearest safe place and get needed rest.

    These are warning signs of fatigue. Do not wait for a crash or a planned stop to act. Get to a safe stopping place and rest before continuing; cab stimulation is not a substitute for sleep.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.2 Driver Factors / fatigue and vision; printed page 2-27, physical PDF page 59; reviewed September 21, 2026. ↗

  18. A driver cannot recall the last several miles and has missed an exit. What is the safest interpretation?

    Correct answer: Fatigue may be affecting awareness and requires a safe stop.

    Missing recent driving memories or signs can be a fatigue warning. The driver should safely stop and address the need for rest, not use another vehicle as a substitute for alertness.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.2 Driver Factors / fatigue and vision; printed page 2-27, physical PDF page 59; reviewed September 21, 2026. ↗

  19. A tired driver feels more awake after coffee and cold air from a window. What should the driver understand?

    Correct answer: Feeling stimulated does not replace the sleep the driver needs.

    Temporary stimulation is not a reliable solution for fatigue. Plan adequate rest and stop safely when drowsy instead of treating a short-lived feeling of alertness as proof of safe driving ability.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.2 Driver Factors / maintaining alertness; printed page 2-28, physical PDF page 60; reviewed September 21, 2026. ↗

  20. Why should a driver avoid darkly tinted glasses when driving at night?

    Correct answer: They reduce the light available for seeing hazards.

    Night driving already offers less visual information. Dark lenses reduce available light further. Do not try to solve glare by making the whole scene darker.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.2 Driver Factors / fatigue and vision; printed page 2-27, physical PDF page 59; reviewed September 21, 2026. ↗

  21. Headlight glare seems worse through a windshield with an oily film inside. What should you do before another night trip?

    Correct answer: Clean both the inside and outside glass surfaces.

    Dirt and film can scatter light and worsen glare. Cleaning inside and outside glass, along with mirrors and lights, helps preserve the limited visibility available at night.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.4 Vehicle Factors / windshield and mirrors; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  22. How should interior cab lighting be managed during night driving?

    Correct answer: Keep it low enough to avoid glare while instruments remain readable.

    Bright interior lighting can interfere with outside vision. Keep instruments readable without unnecessary cab glare, and maintain attention to the road.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.5 Night Driving Procedures; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  23. A truck's headlamps are dirty and one is poorly aimed. What is the right response before driving at night?

    Correct answer: Clean the lamps and have their aim corrected.

    Dirty or misaligned headlamps reduce useful road illumination and may create glare for others. Correct their condition rather than compensating with unsafe following or inappropriate beam use.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.4 Vehicle Factors / headlights; printed page 2-28, physical PDF page 60; reviewed September 21, 2026. ↗

  24. Oncoming high beams make it hard to see. Where should you direct your attention?

    Correct answer: Toward the right side of your lane, without staring at the lights.

    Avoid looking directly into bright oncoming lamps. Use the right side of your lane as a guide while continuing to monitor your path and adjusting speed for the visibility you actually have.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.11.5 Night Driving Procedures; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  25. Which headlight setting generally gives better visibility in fog?

    Correct answer: Low beams, because high beams reflect more light back toward you.

    High beams reflect off fog and can worsen the driver's view. Use low beams and an appropriate reduced speed; better lighting does not remove the need for a safe visibility margin.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.12 Driving in Fog; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  26. Why is following the vehicle ahead's taillights an unreliable way to navigate dense fog?

    Correct answer: That vehicle may stop or leave the roadway without you realizing it.

    Do not blindly follow lights through fog. The other vehicle may be stopped or may have left the roadway. Maintain your own awareness of the road and a safe distance.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.12 Driving in Fog; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  27. Before entering a stretch of very dense fog, you can safely reach a truck stop. What is the safer option if visibility is inadequate?

    Correct answer: Wait at the truck stop until conditions improve.

    When possible, avoid driving in dense fog by waiting in a safe location such as a truck stop or rest area. A roadside stop can expose the truck to vehicles whose drivers cannot see it in time.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.12 Driving in Fog; printed page 2-29, physical PDF page 61; reviewed September 21, 2026. ↗

  28. Which preparation helps keep the windshield usable in freezing conditions?

    Correct answer: Check the defroster, wipers and freeze-protected washer supply.

    Winter preparation includes a working defroster, suitable wipers and washer fluid protected against freezing. Do not start relying on equipment before confirming it can keep your view clear.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.13.1 Vehicle Checks / defrosters, wipers and washers (physical PDF pages 61–62); printed page 2-29–2-30, physical PDF page 62; reviewed September 21, 2026. ↗

  29. Snow and ice cover a truck's steps and handholds. What should happen before using them?

    Correct answer: Clear them so you have secure footing and a reliable grip.

    Winter inspection includes clearing snow and ice from steps and handholds. Secure access reduces the risk of a fall; jumping or relying on eventual melting is not a sound substitute.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.13.1 Vehicle Checks / access and winterfront; printed page 2-30, physical PDF page 62; reviewed September 21, 2026. ↗

  30. After a long drive on a hot day, tire pressure is above its cold reading. Should you bleed air merely to restore the cold reading?

    Correct answer: No. Recheck under the proper cold-inflation conditions.

    Pressure normally rises as a tire heats. Bleeding it to the cold figure while hot can leave it underinflated after cooling. Follow the specified cold-pressure check and stop to investigate overheating.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.14.1 Vehicle Checks / tires and engine coolant; printed page 2-31, physical PDF page 63; reviewed September 21, 2026. ↗

  31. The engine overheats and the cooling system is still hot. What should you do about a pressurized radiator or coolant cap?

    Correct answer: Leave it closed until the system has cooled and follow service instructions.

    Hot pressurized coolant can escape and cause severe burns. Stop safely, allow the system to cool and follow the vehicle's service procedure. A hot cap should not be opened as an immediate cooling shortcut.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.14.1 Vehicle Checks / tires and engine coolant; printed page 2-31, physical PDF page 63; reviewed September 21, 2026. ↗

  32. Why must a driver monitor engine temperature when using a winter front or radiator cover?

    Correct answer: Restricting airflow too much can cause the engine to overheat.

    A winter cover changes cooling airflow. Too much restriction can overheat an engine even in cold weather, so use the proper equipment and monitor temperature.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.13.1 Vehicle Checks / access and winterfront; printed page 2-30, physical PDF page 62; reviewed September 21, 2026. ↗

  33. A railroad crossing has a crossbuck but no active lights or gates. What does the lack of active warnings mean?

    Correct answer: You must use the signs and your own observation to assess trains.

    A passive crossing does not actively warn you with lights or gates. Observe and obey the signs, look and listen, and meet any stopping requirement that applies to your vehicle or load.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.15.1 Types of Crossings; printed page 2-32, physical PDF page 64; reviewed September 21, 2026. ↗

  34. No train horn is audible as you approach a crossing. What can you safely conclude?

    Correct answer: Nothing about whether a train is approaching; look and listen.

    Train horns may not sound at some crossings, and cab noise can mask them. Silence is not permission to cross. Check the tracks and obey the warning devices and applicable stop rules.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.15.3 Driving Procedures; printed page 2-33, physical PDF page 65; reviewed September 21, 2026. ↗

  35. Railroad red warning lights begin flashing while the gate is still upright. What should you do?

    Correct answer: Stop before the tracks rather than trying to beat the gate.

    Stop when the crossing's red lights begin flashing; do not wait for the gate to block the lane. Remain stopped until the gates are up, the lights have stopped and it is safe to cross.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.15.2 Warning Signs and Devices / flashing lights and gates (physical PDF pages 64–65); printed page 2-32–2-33, physical PDF page 65; reviewed September 21, 2026. ↗

  36. One train has just cleared a crossing with several tracks. What must you check before proceeding?

    Correct answer: That no other train is approaching and the crossing warnings permit travel.

    A train on one track may hide a train on another. Check all tracks in both directions and keep obeying the lights and gates; the first train's departure alone does not establish a clear crossing.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.15.3 Driving Procedures; printed page 2-33, physical PDF page 65; reviewed September 21, 2026. ↗

  37. A bus is carrying passengers and is subject to 49 CFR 392.10 at a crossing with no applicable exception. Where must it stop relative to the tracks?

    Correct answer: At least 15 feet but not more than 50 feet away.

    The specified vehicles, including a bus transporting passengers, must stop within the 15-to-50-foot range and look and listen before crossing. Section 392.10 includes specific exceptions; the question excludes those situations.

    Source: 49 CFR 392.10(a), (a)(1) and (b); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  38. For a vehicle required to stop under 49 CFR 392.10, how should the driver select a gear for crossing railroad tracks?

    Correct answer: Choose a gear that completes the crossing without a shift.

    The regulation requires a gear that allows the vehicle to complete the crossing without shifting, and prohibits changing gears while crossing. Avoid creating a loss of power or a stall on the tracks.

    Source: 49 CFR 392.10(a); eCFR title 49 displayed current through September 17, 2026; reviewed September 21, 2026. ↗

  39. Traffic is queued just beyond a railroad crossing, leaving room for your cab but not your full combination. What should you do?

    Correct answer: Wait before the crossing until the whole vehicle can clear it.

    Do not enter unless there is enough space for the entire vehicle to get clear. A combination can be trapped even when the cab has crossed, so evaluate the exit space before committing.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.15.5 Crossing the Tracks; printed page 2-33, physical PDF page 65; reviewed September 21, 2026. ↗

  40. Your vehicle is stuck at a crossing and everyone is safely away from the tracks. What information on the blue-and-white ENS sign helps you alert the railroad?

    Correct answer: Its emergency telephone number and crossing identification number.

    Call the railroad emergency number on the ENS sign, give the crossing identification number and describe the emergency. The ID pinpoints the crossing for the railroad; do not rely on a guessed location or return to the vehicle to make the call.

    Source: FRA, In Case of Emergency, Use ENS Signs To Get Help; FRA page updated April 4, 2025; reviewed September 21, 2026. ↗

  41. Before a long mountain descent, which combination should determine a truck's safe speed?

    Correct answer: Weight, grade length and steepness, road conditions and weather.

    A safe descent speed depends on the vehicle and the actual grade and conditions. A speed that worked on another hill or for another vehicle may not be suitable for this descent.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.16.1 Select a Safe Speed; printed page 2-34, physical PDF page 66; reviewed September 21, 2026. ↗

  42. During a descent, repeated heavy service-brake use leads to less slowing despite more pedal pressure. What is a likely danger?

    Correct answer: Overheated brakes are fading and may no longer control speed.

    Excessive heat can reduce braking effectiveness. Needing more pressure for less slowing is a serious warning, not a reason to keep accelerating or depend on harder pedal pressure to solve the problem.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.16.3 Brake Fading or Failure; printed page 2-34, physical PDF page 66; reviewed September 21, 2026. ↗

  43. Why can poorly adjusted brakes make overheating more likely on a downgrade?

    Correct answer: Some brakes do too little work, overloading the others.

    When some brakes are not doing their share, the others must work harder. That can overheat them and accelerate fade. Correct adjustment and condition matter before starting a descent.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.16.3 Brake Fading or Failure; printed page 2-34, physical PDF page 66; reviewed September 21, 2026. ↗

  44. In the handbook's downgrade example, a suitable low gear is selected and the safe speed is 40 mph. When applying the described snub-braking method, at about what speed are the brakes released?

    Correct answer: 35 mph, about 5 mph below that selected safe speed.

    The handbook describes applying enough braking for a definite slowdown, then releasing around 5 mph below the chosen safe speed and repeating as needed when that safe speed is reached. Forty mph is the example, not a universal mountain speed; proper gear selection and actual conditions remain essential.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.16.4 Proper Braking Technique; printed page 2-34, physical PDF page 66; reviewed September 21, 2026. ↗

  45. Your truck is gaining speed on a steep descent because its brakes have failed. An escape ramp is ahead. What should guide your decision?

    Correct answer: Use the available ramp rather than delay while speed builds.

    Escape ramps are intended to help stop runaway vehicles. Know their locations and use an available ramp when brakes fail rather than letting the truck gather more speed while searching for a less inconvenient option.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.3 Brake Failure on Downgrades; printed page 2-36, physical PDF page 68; reviewed September 21, 2026. ↗

  46. A driver says a heavily loaded truck can always descend a hill in the same gear it used to climb. Is that a reliable rule for modern trucks?

    Correct answer: No. Engine and braking characteristics can require a lower descent gear.

    The handbook warns against relying on the old same-gear rule for every truck. Select the appropriate low gear before descending, considering the vehicle and grade rather than applying a universal uphill-to-downhill shortcut.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.16.2 Select the Right Gear; printed page 2-34, physical PDF page 66; reviewed September 21, 2026. ↗

  47. A driver steers around an obstacle with enough room to avoid it. Why should the driver avoid turning the wheel much farther than necessary?

    Correct answer: Excessive steering can lead to a skid or rollover.

    Emergency steering must be controlled. A heavy vehicle can skid or roll if the driver overcorrects. Steer only as much as needed and retain control of the vehicle's return path.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.1 Steering to Avoid a Crash; printed page 2-35, physical PDF page 67; reviewed September 21, 2026. ↗

  48. You have safely steered onto a clear shoulder to avoid a collision, and there is room to stop. What is generally safer than immediately jerking back onto the road?

    Correct answer: Stay on the shoulder until stopped and return when safe.

    When the shoulder provides a safe stopping path, stopping there avoids a sudden uncontrolled return. Do not assume every shoulder can support a truck; evaluate its surface, obstacles and available space.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.1 Steering to Avoid a Crash; printed page 2-35, physical PDF page 67; reviewed September 21, 2026. ↗

  49. A truck with hydraulic brakes loses pedal pressure. Which temporary response does the handbook describe as sometimes rebuilding enough pressure to help stop?

    Correct answer: Pumping the hydraulic brake pedal.

    For hydraulic pressure loss, pumping the pedal may build temporary pressure. This is not an instruction for air brakes or normal ABS operation. Stop safely and have the fault corrected; a temporarily firmer pedal does not make the truck serviceable.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.3 Loss of Hydraulic Pressure; printed page 2-36, physical PDF page 68; reviewed September 21, 2026. ↗

  50. A front tire blows out, but no immediate collision requires emergency braking. What should you do first?

    Correct answer: Hold the wheel firmly and let the truck slow without hard braking.

    A blowout can pull or destabilize the truck. Keep a firm grip, avoid braking initially unless needed to avoid an immediate collision, and slow before braking gently and stopping safely.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.4 Tire Failure; printed page 2-37, physical PDF page 69; reviewed September 21, 2026. ↗

  51. You hear a tire burst but the truck still seems to handle normally. What should happen after you reach a safe stopping place?

    Correct answer: Inspect all tires because one tire in a dual pair may have failed.

    A dual tire can fail without dramatic handling changes. Do not assume normal steering proves the tires are sound; stop safely and check all tires.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.17.4 Tire Failure; printed page 2-37, physical PDF page 69; reviewed September 21, 2026. ↗

  52. What is the main benefit of functioning ABS during hard braking?

    Correct answer: It reduces wheel lock so the driver can retain more steering control.

    ABS helps prevent wheels from locking during braking and can help preserve control. It does not create traction, guarantee a shorter stop or justify higher speeds and smaller gaps.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.18.4 How ABS Helps You; printed page 2-38, physical PDF page 70; reviewed September 21, 2026. ↗

  53. An ABS warning lamp remains on after its normal self-check or comes on while driving. What does that suggest?

    Correct answer: An ABS fault may exist; normal brakes may still work, but service is needed.

    A warning beyond normal startup behavior can indicate an ABS problem. With otherwise sound brakes, conventional braking remains, but ABS assistance may be lost. Have the problem serviced and do not confuse the normal initial lamp check with a fault.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.18.7 Braking If ABS Is Not Working; printed page 2-38, physical PDF page 70; reviewed September 21, 2026. ↗

  54. A tractor has functioning ABS but its trailer does not. Is the tractor's ABS still useful?

    Correct answer: Yes. It can help retain tractor control even without trailer ABS.

    ABS can still offer benefits on the part of the combination that has it. Tractor ABS does not make an unequipped trailer an ABS trailer, so avoid assuming identical anti-lock protection throughout the combination.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.18.5 ABS on the Tractor Only or Only on the Trailer; printed page 2-38, physical PDF page 70; reviewed September 21, 2026. ↗

  55. In a straight-line emergency stop with properly functioning ABS on all axles, how should the driver generally use the service brake?

    Correct answer: Apply firm, steady pressure without pumping the pedal.

    With functioning ABS, use the braking needed while letting the system manage wheel lock. Pumping or routine stab braking interrupts the intended operation; ABS still does not remove traction and stopping-distance limits.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.18.6 Braking with ABS; printed page 2-38, physical PDF page 70; reviewed September 21, 2026. ↗

  56. A truck's front tires have lost grip and it continues straight despite steering input. Will turning the wheel much farther solve the skid?

    Correct answer: No. Reduce the excessive speed or braking input so traction can return.

    In a front-wheel skid, the tires cannot provide the requested steering force. More steering alone does not restore grip. Ease the excessive input causing the skid and slow as safely as possible.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.19.3 Front-wheel Skids; printed page 2-39, physical PDF page 71; reviewed September 21, 2026. ↗

  57. Why can locked tractor drive wheels during braking develop into a jackknife?

    Correct answer: The trailer can push the tractor's sliding rear end sideways.

    Locked drive wheels have little directional control. The trailer can push the tractor's rear out of line, folding the combination. Prevent wheel lock and use braking appropriate to the vehicle and conditions.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.19.1 Drive-wheel Skids; printed page 2-39, physical PDF page 71; reviewed September 21, 2026. ↗

  58. You stop to help at a crash and can choose a safe place to park. Why should you stay clear of the immediate crash area?

    Correct answer: Emergency vehicles need access and another collision must be avoided.

    Protect the area from further collisions without blocking responders. Park safely away from the immediate scene, warn traffic as appropriate and provide the location when calling for help.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.20.1 Protect the Area; printed page 2-40, physical PDF page 72; reviewed September 21, 2026. ↗

  59. Smoke indicates a truck fire and the vehicle can still be stopped safely. Which location is preferable?

    Correct answer: An open area away from buildings, brush and other vehicles.

    Stop off the road in a suitable open area when possible, away from things that can catch fire, and notify emergency services. A fuel station is an especially unsuitable place to take a burning vehicle.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-40, physical PDF page 72; reviewed September 21, 2026. ↗

  60. After stopping safely for an engine fire, what should you avoid?

    Correct answer: Opening the hood and feeding the fire with more air.

    Stop the engine as soon as you can safely do so. Avoid opening the hood, which can supply oxygen and intensify a fire. Prioritize getting clear and contacting emergency services over attempting risky access.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-40, physical PDF page 72; reviewed September 21, 2026. ↗

  61. Smoke is coming from inside a closed box trailer. Why should the driver keep the cargo doors shut?

    Correct answer: Opening them can add oxygen and make the fire flare up.

    Opening a burning cargo compartment can rapidly feed the fire. Keep the doors closed, stay clear and call emergency services, especially when the cargo may include hazardous materials.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-41, physical PDF page 73; reviewed September 21, 2026. ↗

  62. You do not know what is burning in a load that may contain hazardous materials or which extinguisher is suitable. What should you do?

    Correct answer: Keep clear and let trained firefighters handle the fire.

    The wrong extinguishing method can worsen a fire or create another hazard. If the material or suitable agent is uncertain, keep clear, notify responders and leave the response to trained firefighters.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-41, physical PDF page 73; reviewed September 21, 2026. ↗

  63. A trained person has judged a small fire safe to tackle with a suitable extinguisher and a clear escape route. Where should the discharge be aimed?

    Correct answer: At the base or source of the fire.

    An extinguisher must act on the source of the fire rather than just its upper flames. This does not mean approaching a large, unknown or unsafe fire; leave when conditions are unsafe and call emergency services.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-41, physical PDF page 73; reviewed September 21, 2026. ↗

  64. Visible flames and smoke have stopped after a vehicle fire. What should a driver remember?

    Correct answer: Hot material can reignite; the absence of flames is not an all-clear.

    Material may remain hot and reignite even when flames or smoke are no longer visible. Do not treat that appearance as permission to resume driving; keep clear and follow the emergency response and inspection process.

    Source: South Carolina Commercial Driver's License Manual, posted 179-page PDF, body version March 2025; 2.21.3 Fire Fighting; printed page 2-41, physical PDF page 73; reviewed September 21, 2026. ↗

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Study questions checked against SCDMV licensing information, its posted CDL manual and cited federal rules. Review date: September 21, 2026. This is selected study coverage, not a complete course. Follow the cited source and the actual vehicle manufacturer’s procedure; equipment and brake-system differences matter. These quizzes do not replace supervised inspection or hands-on training.