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30 multiple-choice questions and 11 flashcards on General Knowledge — Hazard Perception and Emergencies, about 10% of the CDL Class A bank. Every one carries a written rationale.
General Knowledge — Hazard Perception and Emergencies is one of 12 chapters in CoStudy's CDL Class A (General Knowledge) bank, and it holds 30 of the bank's 300 multiple-choice questions — roughly 10% of the total. That proportion is not arbitrary: chapters follow the certifying body's published exam outline, and the number of questions in each is set by that domain's published weight, so the share of your practice time this chapter takes matches the share of the real exam it accounts for.
Studying by chapter is worth doing once you have a diagnostic score. A single overall percentage tells you whether you are close; it does not tell you which domain is dragging. Working a weak chapter in isolation, and re-testing it in isolation, is the fastest way to move a score that has stalled — and it is why the mock exams in CoStudy report by domain rather than as one number.
10 questions drawn from this chapter, with the full rationale shown — the controlling principle behind the right answer, and why each wrong option tempts and fails.
Which vehicle must stop at every railroad crossing even when no train is in sight and no signal is active?
Answer: D — A bus carrying passengers or a vehicle carrying placarded hazardous material
D) Correct — passenger-carrying buses and placarded hazardous material vehicles are the categories required to stop at crossings. B) Length affects how you judge clearance across the tracks but does not trigger a mandatory stop. C) Weight class determines licensing, not the crossing stop requirement. A) Manual transmissions mean you must not change gears while on the tracks, which is a different rule entirely.
A driver approaching an intersection sees a parked car with its front wheels turned outward and an occupant in the driver's seat. What is the BEST interpretation?
Answer: B — The car is likely to pull into the lane and should be treated as a hazard now
B) Correct — an occupied vehicle with wheels turned toward the lane is a classic early clue, and the time to plan is before it moves. A) Turned wheels are a hill-parking practice, but pairing them with an occupant is what makes this a clue, so the statement is true yet beside the point. C) Assuming another driver sees you is the assumption hazard perception is meant to remove. D) Waiting for brake lights gives up the seconds that early recognition buys you.
A driver's vehicle becomes disabled on a divided highway. Where should the three warning devices be placed?
Answer: C — Ten feet behind the vehicle and one hundred feet behind it in the same direction
C) Correct — on a divided or one-way roadway all three go toward approaching traffic: about ten feet, one hundred feet, and two hundred feet back. A) Placing one ahead is the undivided two-lane pattern, applied to the wrong road type. B) Two hundred feet back is one of the distances, but the other two devices are omitted. D) This reverses the direction of the spacing and puts warnings where no traffic is approaching from.
If a truck tire catches fire, you should:
Answer: C — Stop, distance yourself, and call emergency responders — tire fires can re-ignite and emit toxic fumes
A) Worsens fire. B) Dangerous and slow. C) Correct — tire fires are difficult to extinguish, can re-ignite, and produce toxic smoke; trained responders needed. D) Insufficient for tire fire.
A fire starts in an electrical panel behind the dash. Which extinguisher rating is appropriate?
Answer: B — A B:C or A:B:C rated extinguisher aimed at the base of the fire
B) Correct — energized electrical fires are class C, and a B:C or A:B:C unit is what handles them safely. A) An A-only unit is water based and conducts current back to the operator. C) Water on an energized circuit is the specific hazard the class C rating exists to prevent. D) Ratings match the fuel type; treating them as optional is a common and dangerous misconception.
Federal regulations prohibit CMV drivers from:
Answer: A — Texting while driving and using a hand-held mobile phone
A) Correct — texting and hand-held mobile phone use are federally prohibited; violations carry steep penalties. B/C/D) Not prohibited.
If your engine catches fire, you should:
Answer: B — Park, shut off the engine, and stay away from the hood; use extinguisher through grille if possible
A) Opening hood feeds oxygen to fire, intensifying it. B) Correct — never open hood; fight from below or through grille. C) Dangerous. D) Wrong agent for oil/electrical.
On a divided highway, the third warning triangle should be placed:
Answer: C — Approximately 200 feet behind the truck
A) Too close. B) That's the second triangle distance. C) Correct — on undivided road: 10/100/100 toward traffic. On divided/one-way: 10/100/200 feet behind. D) Useless placement.
Hazard flashers should be used:
Answer: A — When your vehicle is moving slowly and creating a hazard, or stopped on/near a road
A) Correct — flashers alert others to slow/stopped traffic hazards. B) Illegal while moving normally in many states. C/D) Use turn signals.
If you feel drowsy on the road, you should:
Answer: B — Pull over at a safe location and sleep
A) Dangerous. B) Correct — fatigue is impairment; the only safe response is to stop and rest. C) Temporary fixes only. D) Worst response.
4 cards from the 11 in this chapter.
What is controlled braking and when is it used?
Applying the brakes firmly without locking the wheels, keeping steering control; used in emergency stops where you must also steer, and where wheel lockup would cause a skid.
Why must a driver never change gears while crossing railroad tracks?
A missed shift can stall the vehicle on the tracks. Select a gear before the crossing that will pull the whole vehicle across without shifting, and never start across unless there is room to clear the far rail completely.
Name four clues that a driver ahead may be about to do something hazardous.
Drifting within the lane • slow response to traffic changes • hands not visible or head turned away • sudden braking without cause • vehicle stopped at an odd angle or on the shoulder.
What should a driver do if the vehicle drifts off the pavement onto the shoulder?
Stay on the shoulder, hold the wheel firmly, ease off the accelerator, brake gently, then when speed is safe turn back onto the pavement sharply and countersteer immediately once both front wheels are back on.
These are a sample. The full General Knowledge — Hazard Perception and Emergencies chapter runs 41 items with per-chapter progress tracking, on the web and in the iOS app.