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40 multiple-choice questions and 21 flashcards on General Knowledge — Safe Driving and Vehicle Control, about 13% of the CDL Class A bank. Every one carries a written rationale.
General Knowledge — Safe Driving and Vehicle Control is one of 12 chapters in CoStudy's CDL Class A (General Knowledge) bank, and it holds 40 of the bank's 300 multiple-choice questions — roughly 13% 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.
5 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.
If you start to hydroplane, your first action should be:
Answer: C — Release the accelerator and avoid braking
A) Braking can cause skid. B) Sharp steering loses control. C) Correct — release throttle, do not brake; the vehicle slows and tires regain contact. Use clutch on manual transmission. D) Increases hydroplane risk.
Headlights should be used:
Answer: C — Half-hour after sunset to half-hour before sunrise, and any time visibility is reduced
A) Too narrow. C) Correct — also required in rain, fog, snow, dust, smoke, or any reduced-visibility condition. C/D) Misconceptions.
If caught in a high crosswind, you should:
Answer: D — Reduce speed and grip the wheel firmly; be ready for sudden gusts
A) Increases rollover risk. D) Correct — slower speed and firm steering control; empty trailers are especially vulnerable. C) Illegal and dangerous. B) Engine brake unrelated to wind.
Total stopping distance for a fully loaded tractor-trailer at 55 mph on dry pavement is approximately:
Answer: C — 300+ feet (perception + reaction + brake lag + braking)
A/B/D) Underestimate the four-stage distance. C) Correct — perception ~60 ft + reaction ~60 ft + brake lag ~32 ft + effective braking ~170 ft ≈ 300+ ft. Off-by-one trap: drivers think in car-distances.
Progressive shifting means:
Answer: B — Shifting at lower RPMs in lower gears and higher RPMs in higher gears for fuel efficiency
A) Backward. B) Correct — progressive shifting saves fuel by using less RPM in lower gears (less load), more in higher (more load). C/D) Misconceptions.
4 cards from the 21 in this chapter.
What is total stopping distance and what three components make it up?
The distance from seeing a hazard to a full stop: perception distance plus reaction distance plus braking distance. At highway speed a loaded truck needs far more room than a car.
What is the safest action when fog reduces visibility to near zero?
Get off the road and park in a safe area away from travel lanes, turning on four-way flashers. If you must drive, use low beams and fog lights, slow down, and use the right edge line as a guide.
Following distance rule for trucks over 40 mph?
Same base + 1 additional second.
Hydroplaning starts at what depth + speed?
As little as 1/12 inch of water at 30+ mph.
These are a sample. The full General Knowledge — Safe Driving and Vehicle Control chapter runs 61 items with per-chapter progress tracking, on the web and in the iOS app.