Vehicle Equipment & Safe Operation — Ohio
Ohio CDL practice test: 388 free practice questions (Based on the official driver handbook). The official format is not yet verified; check the official site before your test. Vehicle Equipment & Safe Operation: 146 questions.
Brakes, tires, lights, mirrors, seat belts, child seats and basic vehicle control.
This topic page is still being reviewed against the official handbook. Until review is finished it is hidden from search engines.
| Topic / Metric | Value |
|---|---|
| Topic | Vehicle Equipment & Safe Operation |
| License test | Ohio CDL permit (CLP) knowledge tests |
| Topic questions | 146 (38% of 388 total) |
| Review status | This topic page is still being reviewed against the official handbook. Until review is finished it is hidden from search engines. |
Official handbook
Not yet verified
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Questions (146)
1. If the emergency air line loses pressure:
- The service brakes will activate.
- The tractor protection valve will close. ✓
- The rear trailer will detach from the combination.
Answer: B. The tractor protection valve will close.
The tractor protection valve will close when the emergency air line loses pressure. The handbook says the tractor protection valve keeps air in the tractor when a trailer breaks away or has a bad leak. It closes by itself when air pressure drops, stopping air from leaving the tractor and letting air out of the trailer emergency line. That release brings on the trailer emergency brakes. So a low-pressure emergency line points to the tractor protection valve closing, not to service brakes or trailer separation.
2. A driver should use the trailer hand valve to:
- Uncouple the trailers.
- Test the trailer brakes. ✓
- Apply the emergency brakes.
Answer: B. Test the trailer brakes.
The trailer hand valve is used to test the trailer brakes. The handbook describes the trailer hand valve, also called the trolley valve or Johnson bar, as a control that operates the trailer brakes. Its only intended use is checking those brakes. The same section warns against using it while driving because it can cause the trailer to skid, and it says not to use it for parking. Another passage describes testing trailer service brakes by applying them with the hand control and feeling them engage. That supports using the hand valve as a test control.
3. A driver can rely on front wheel braking to work:
- On dry roadways only.
- Under all conditions. ✓
- Under all conditions, except for snow.
Answer: B. Under all conditions.
4. When turning, when should the turn signal be canceled?
- Before entering the turn
- During the turn
- After the turn is completed ✓
Answer: C. After the turn is completed
Cancel the turn signal after the turn is completed. The handbook says to signal continuously and not cancel the signal until you have completed the turn. It also says to turn off the signal after you have turned, or cancel it upon completion of a turn or lane change. So the signal stays on through the whole turn and is switched off once the turn is finished.
5. An alcohol evaporator in an air brake system:
- Makes the brakes work without squeaking.
- Prevents ice from forming in the braking system. ✓
- Lubricates parts of the braking system.
Answer: B. Prevents ice from forming in the braking system.
An alcohol evaporator prevents ice from forming in the braking system. The handbook explains that some air brake systems carry an alcohol evaporator, which sends alcohol into the air system. In cold weather this lowers the chance that ice will build up in air brake valves and other parts. The same section notes that ice inside the system can stop the brakes from working. That matches the choice about preventing ice formation; the device is there for cold-weather protection of the air brake system.
6. Having ABS on only one axle:
- Can be dangerous.
- Still allows you additional control when braking. ✓
- Slows the vehicle, but cannot stop it.
Answer: B. Still allows you additional control when braking.
Having ABS on only one axle still gives you more control over the vehicle while braking. The handbook says that ABS on only the tractor, only the trailer, or even only one axle still gives you more control during braking. It explains that ABS helps prevent wheel lockup, and locked wheels can cost you steering control or cause a skid or jackknife. It also says ABS may or may not shorten stopping distance, so the point is control, not faster stopping. For that reason, partial ABS is described as useful, and you should brake normally rather than treating it as dangerous.
7. If corrosive materials leak in a trailer, the trailer should be:
- Cleaned with acid.
- Cleaned with water. ✓
- Left to air dry without washing.
Answer: B. Cleaned with water.
When corrosive materials leak in a trailer, the trailer needs to be cleaned with water. The hazardous materials section covers Class 8 corrosive materials and says that any part of the vehicle that a corrosive liquid touched has to be washed well with water. It also tells you to wash out the inside of the trailer as soon as you can after unloading, before you load anything else. So the cleanup job is a water wash, not a waiting period and not a different chemical.
8. To use the controlled braking method, you should:
- Lock your wheels while braking.
- Apply your brakes as firmly as possible without locking the wheels. ✓
- Slightly tap the brakes.
Answer: B. Apply your brakes as firmly as possible without locking the wheels.
To use controlled braking, apply your brakes as firmly as possible without locking the wheels. The handbook describes controlled braking as applying the brakes as hard as you can without locking the wheels. It also says to keep steering wheel movements very small while braking. If you need a larger steering adjustment or the wheels lock, release the brakes and re-apply as soon as you can. This method is meant to keep the vehicle straight and let you turn if needed. Locking the wheels is tied to skidding, and a skidding vehicle cannot be controlled.
9. Which of the following is acceptable if found during a pre-trip inspection?
- Mismatched tire sizes
- Tread of 3/32 of an inch in the grooves of the front tires
- Tires manufactured by different makers ✓
Answer: C. Tires manufactured by different makers
10. When traveling down a steep downgrade:
- The air brakes should be used.
- The vehicle should be placed in a low gear and the driver should use engine braking. ✓
- The driver should continually downshift instead of using the brakes.
Answer: B. The vehicle should be placed in a low gear and the driver should use engine braking.
On a steep downgrade, you should place the vehicle in a low gear and use engine braking, with the brakes only as a supplement. On a long or steep downgrade, the handbook says the brakes are only a supplement to the engine's braking effect. You first get the vehicle into the proper low gear, then use the brakes in a controlled way to keep speed near a safe speed. That is why the low-gear and engine-braking choice fits: the engine does most of the speed control, and the brakes help rather than carry the whole job. The handbook also warns that brakes can fade if they get too hot from overuse.
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Last checked: 2026-10-17 · Verified from official source
Updated: · Based on the official driver handbook