CDL General Knowledge Test · CDL General Knowledge Test
CDL General Knowledge Test: Emergencies, Skids, Crashes, and Fires Concepts
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Overview
This chapter covers what to do when something goes wrong suddenly: another vehicle in your path, a brake or tire failure, a skid, a crash, or a fire. Good habits help prevent emergencies, but when one happens, your chances depend on how well you act.
You can usually turn to miss an obstacle faster than you can stop. Keep both hands on the wheel, do not brake while turning, and be ready to countersteer. If an oncoming driver drifts into your lane, a move to the right is usually best. For emergency stops, use controlled braking or stab braking instead of jamming on the brakes. If a tire blows, hold the wheel firmly and stay off the brake until you slow down.
ABS keeps wheels from locking so you can steer, but it does not always shorten stopping distance. Most skids come from driving too fast for conditions. At a crash, protect the area, notify authorities, and care for the injured. For a fire, pull off in an open area, keep van doors closed for a cargo fire, and aim the extinguisher at the base of the fire from upwind.
Key concepts
Emergency steering
Turning around an obstacle is usually faster than stopping. Do not brake while turning, turn only as much as needed, and countersteer once you are past the obstacle.
Memory tipSteer and countersteer are one move.
Controlled and stab braking
Controlled braking: brake as hard as you can without locking the wheels. Stab braking: brake fully, release when the wheels lock, and reapply when they roll again.
Memory tipNever just jam the pedal and hold it.
Tire failure
Signs are a loud bang, heavy vibration, or heavy steering. Hold the wheel firmly, stay off the brake until the vehicle slows, then brake gently, pull off, and check all tires.
Memory tipGrip the wheel, not the brake.
Antilock brakes (ABS)
A computer system that keeps wheels from locking during hard braking so you can keep steering. It does not always shorten stopping distance, and if it fails you still have normal brakes.
Memory tipABS is for control, not a shorter stop.
Skid recovery
For a drive-wheel braking skid, stop braking, steer quickly where you want to go, then countersteer. For a front-wheel skid, stop turning and braking so hard and let the vehicle slow down.
Memory tipRelease the brake first in a skid.
Fighting a vehicle fire
Pull off in an open area away from buildings and fuel, and call for help. Keep van doors shut for a cargo fire. Stand upwind, stay back, and aim at the base of the fire. Do not use water on electrical or gasoline fires.
Memory tipUpwind, at the base, doors closed.
Often tested
- You can usually turn to miss an obstacle faster than you can stop.
- If an oncoming driver drifts into your lane, steer right.
- After a blowout, hold the wheel firmly and stay off the brake.
- ABS helps you steer, but it does not always shorten stopping distance.
- At a crash: protect the area, notify authorities, care for the injured.
- Aim the extinguisher at the base of the fire.
3 sample questions
Verified practice questions from this unit.
Question 1. One of your tires blows out. What should you do right away?
- ① Brake hard right away to stop quickly
- ② Steer onto the shoulder at full speed
- ③ Hold the steering wheel firmly and stay off the brake until the vehicle slows
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Answer: ③ Hold the steering wheel firmly and stay off the brake until the vehicle slows
Key point: Blowout: grip the wheel, stay off the brake
When a tire fails: hold the steering wheel firmly with both hands and stay off the brake unless you are about to hit something. Once the vehicle slows, brake very gently, pull off the road, and check all the tires.
Wrong choices
- Brake hard right away to stop quickly: Braking after a blowout can make you lose control.
- Steer onto the shoulder at full speed: Quick moves at full speed can cause a rollover or skid.
Question 2. In an emergency, which can you almost always do faster?
- ① Turn to miss the obstacle
- ② Stop before reaching the obstacle
- ③ Both take the same amount of time
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Answer: ① Turn to miss the obstacle
Key point: Turning usually beats stopping
Stopping is not always the safest choice. You can almost always turn to miss an obstacle more quickly than you can stop. But top-heavy vehicles and multiple trailers may flip over.
Wrong choices
- Stop before reaching the obstacle: A large vehicle needs a long distance to stop.
- Both take the same amount of time: Turning is usually quicker than stopping.
Question 3. What are the three basic steps at any crash scene?
- ① Move the injured, clean up the road, and leave
- ② Protect the area, notify authorities, and care for the injured
- ③ Take photos, call your employer, and wait in the cab
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Answer: ② Protect the area, notify authorities, and care for the injured
Key point: Crash: protect, notify, care
At any crash, protect the area (move your vehicle off the road if you can, use flashers, set out triangles), notify authorities, and care for the injured.
Wrong choices
- Move the injured, clean up the road, and leave: Do not move badly injured people unless there is fire or traffic danger.
- Take photos, call your employer, and wait in the cab: Protecting the area to prevent another crash comes first.