Iowa CDL — General Knowledge practice
Iowa CDL — General Knowledge: Handling Emergencies practice test
What to do when things go wrong — brake failure, tire blowouts, skids, and stalling on railroad tracks.
Content reviewed against official driver handbooks · August 12, 2026
15 questions · pass with 12 correct. You get instant feedback and an explanation after every answer.
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12 sample Handling Emergencies questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
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1. Where does the manual say is the best place to practice recovering from a skid?
Correct answer: At a big driving range or on a skid pad
Staying off the brake, turning the wheel quickly, pushing in the clutch, and counter-steering take lots of practice, and the best setting for it is a big practice range or a skid pad.
Source: Iowa Commercial Driver's License Manual — Section 2.19.2, Correcting a Drive-wheel Braking Skid
2. Which hydraulically braked trucks and buses must have ABS?
Correct answer: Those rated at 10,000 pounds GVWR or more and manufactured from March 1, 1999 on
The DOT requires ABS on hydraulically braked trucks and buses rated 10,000 pounds or more that were built starting March 1, 1999.
Source: Iowa Commercial Driver's License Manual — Section 2.18.2, Vehicles Required to Have Antilock Braking Systems
3. Which statement about antilock brakes is correct?
Correct answer: ABS won't make up for bad brakes or poor brake maintenance
Antilock brakes supplement your regular brakes rather than replacing them. They won't compensate for bad brakes, won't prevent power or turning skids, and doesn't allow closer following.
Source: Iowa Commercial Driver's License Manual — Section 2.18.8, Safety Reminders
4. Only your trailer has ABS. While braking, you lose steering control or the tractor starts to jackknife. What should you do?
Correct answer: Let up on the brakes, if it's safe, until you regain control
Trailer-only ABS makes the trailer less prone to swinging out, but should steering control slip away or the tractor start to jackknife, ease off the brakes when it's safe until you have control again.
Source: Iowa Commercial Driver's License Manual — Section 2.18.5, ABS on the Tractor Only or Only on the Trailer
5. On a combination with electric trailer brakes, what happens if the electrical connection to the trailer is lost?
Correct answer: The trailer loses all of its braking and control
Losing the electrical connection on an electric-brake trailer means the towed unit loses all braking and control, which can lead to a crash.
Source: Iowa Commercial Driver's License Manual — Section 11.6.1, Combination Vehicles Only
6. Your vehicle catches fire. Which of these places should you NOT pull into?
Correct answer: A service station
Pull off the road onto open ground clear of buildings, trees, brush, and other vehicles, and stay out of service stations. Then notify emergency services.
Source: Iowa Commercial Driver's License Manual — Section 2.21.3, Fire Fighting
7. Besides reducing braking friction, what risk does grease or oil on the brakes create?
Correct answer: A fire hazard
Contaminants on brake linings, pads, drums, or discs reduce braking friction and can contribute to a crash, and they also pose a fire hazard.
Source: Iowa Commercial Driver's License Manual — Section 11.5.2, Axle Components/Steering Axle
8. During a school bus inspection, you find the seal on the first aid kit broken. What could that mean?
Correct answer: Items may be missing from the kit
The first aid kit and the body fluid cleanup kit must both be present with their seals intact, because a broken seal can mean something has been taken out.
Source: Iowa Commercial Driver's License Manual — Section 11.3, School Bus Only
9. Your truck stalls on the tracks and no train is in sight. What does Iowa's manual say to do?
Correct answer: Have everyone leave the vehicle and move well away at once, train or no train
If you get stuck or stall on a crossing, get everyone out and well away right away, train or no train, then phone the number posted on the crossing's ENS sign (or 911 if there isn't one).
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Make Safe Choices
10. Later in your trip, you come upon a crash involving an aggressive driver who passed you earlier. What does the manual say to do?
Correct answer: Stop a safe distance from the scene, wait for police, and report what you saw
If an aggressive driver crashes ahead, stop well clear of the scene, wait for police to arrive, and describe the driving behavior you witnessed.
Source: Iowa Commercial Driver's License Manual — Section 2.10.3, What You Should Do When Confronted by an Aggressive Driver
11. A small fire breaks out in your cab's electrical wiring. According to the manual's fire guidance, which extinguishing agent must you NOT use?
Correct answer: Water
Class C (electrical) fires need an agent that won't carry current, like carbon dioxide or a dry chemical. Water can shock you on an electrical fire, though it's fine for burning wood, paper, or cloth.
Source: Iowa Commercial Driver's License Manual — Section 2.21.3, Fire Fighting
12. Which class of fire involves burning metals and is put out with specialized extinguishing powders?
Correct answer: Class D
The fire class table lists Class D as combustible metals, extinguished with specialized powders. Class A is ordinary combustibles, B is greasy liquids, and C is electrical.
Source: Iowa Commercial Driver's License Manual — Section 2.21.3, Fire Fighting (Figure 2.20, Class/Type of Fires)
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