Vehicle Equipment & Safe Operation — District of Columbia
District of Columbia CDL practice test: 423 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: 177 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 | District of Columbia CDL permit (CLP) knowledge tests |
| Topic questions | 177 (42% of 423 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
Advertisement
Questions (177)
1. In general, when loading a tank with flammable liquids:
- The engine should be running.
- A ground should be established before opening the filling hole. ✓
- A ground should be broken right before opening the filling hole.
- The filling hole should be locked during loading.
Answer: B. A ground should be established before opening the filling hole.
When loading a tank with flammable liquids, establish a ground before you open the filling hole. The handbook's flammable liquids section says to turn off the engine before loading, then ground the cargo tank correctly before filling it through an open filling hole. It spells out the order: ground the tank before opening the filling hole, and keep that ground in place until after the filling hole is closed again. That sequence is what the bank answer describes, so the ground has to be set before the hole is opened, not broken then.
2. Brake pads should:
- Be covered with grease.
- Be covered with oil.
- Be covered with brake fluid.
- Not have any oil or grease on them. ✓
Answer: D. Not have any oil or grease on them.
Brake pads should not have any oil or grease on them. The handbook lists shoes or pads with oil, grease, or brake fluid on them as a bad brake condition. It also says contaminants like grease and oil can reduce braking friction and may create a fire hazard. That is why brake pads are inspected for contamination and should stay clean rather than coated with anything slippery.
3. During the steering box portion of the vehicle inspection test, you should not:
- Ensure that the steering box is securely mounted.
- Ensure that the steering box is free of leaks.
- Look for missing bolts in the steering box.
- Assume all cotter keys are present. ✓
Answer: D. Assume all cotter keys are present.
You should not assume all cotter keys are present; you need to check for missing cotter keys or pins in the steering connections. The handbook says to inspect the visible steering connections and make sure there are no missing nuts, bolts, or cotter keys/pins. It also lists missing cotter keys as a steering system defect. That means cotter keys are something you verify during the inspection, not something you take for granted. Assuming they are all present skips the check the handbook calls for.
4. Hydraulic brakes can fail for one of two reasons. Which of the following is one of those reasons?
- There is a loss of hydraulic pressure. ✓
- You are driving uphill.
- The brakes get too cold.
- The brakes are used too much in one day.
Answer: A. There is a loss of hydraulic pressure.
One reason hydraulic brakes can fail is a loss of hydraulic pressure. The Texas CDL handbook lists two common causes of hydraulic brake failure: losing hydraulic pressure and brake fade on long hills. It describes a pressure loss as the system not building pressure, with a spongy pedal or a pedal that sinks to the floor. Since the question asks for one of those two reasons, the loss of hydraulic pressure is the correct choice. The other choices are not among the two causes the handbook gives.
5. Once stopped as part of the stop/start maneuver, you should:
- Apply the parking brake. ✓
- Keep the vehicle in first gear.
- Be perpendicular to the curb.
- Be blocking a driveway.
Answer: A. Apply the parking brake.
6. Braking mechanisms are located ____ a brake drum.
- Outside
- Inside ✓
- Next to
- On top of
Answer: B. Inside
The braking mechanism sits inside the brake drum. The handbook describes the s-cam drum brake, the most common foundation brake, and says plainly that the braking mechanism is inside the drum. The wheels are bolted to the drums at each end of the axles, and to stop, the brake shoes and linings are pushed against the inside of the drum. That contact creates the friction that slows the vehicle and builds heat. So the working parts that squeeze and rub are housed within the drum, not mounted around it.
7. Dollies equipped with ABS are required to have malfunction lamps located where?
- On the rear
- On the left side ✓
- On the front
- On the top
Answer: B. On the left side
Dollies equipped with ABS are required to have their malfunction lamp on the left side. The handbook states that dollies manufactured on or after March 1, 1998, must have an ABS malfunction lamp on the left side. It also describes trailer ABS malfunction lamps as yellow and located on the left side, at either the front or rear corner. For dollies, the required location given is the left side. That lamp is the warning that something in the ABS is not working.
8. During the vehicle inspection test, you will be required to do all of the following, except:
- Walk around the vehicle.
- Point to or touch each item.
- Explain what you are checking and why.
- Crawl under the vehicle. ✓
Answer: D. Crawl under the vehicle.
You will not have to crawl under the vehicle during the CDL vehicle inspection test. The handbook says you must walk around and get in and out of the vehicle to inspect it. For each safety critical item, you must identify it by naming it and pointing to or touching it, then explain what you are checking and why. If you skip that show-and-tell, you get no credit for the item. The same passage directly states that crawling under the vehicle is not required, so that action is the exception among the choices.
9. A combination vehicle has:
- One air line.
- Two air lines. ✓
- Three air lines.
- Four air lines.
Answer: B. Two air lines.
A combination vehicle has two air lines: the service line and the emergency line. The handbook says every combination vehicle has exactly two air lines running between the vehicles. One is the service line, also called the control or signal line, and its pressure changes with the foot brake or trailer hand brake. The other is the emergency line, also called the supply line, which supplies air to the trailer tanks and controls the emergency brakes. Because the handbook names these two lines, the correct count is two.
10. Most heavy-duty vehicles use:
- Single air brake systems.
- Dual air brake systems. ✓
- Triple air brake systems.
- Quadruple air brake systems.
Answer: B. Dual air brake systems.
Most heavy-duty vehicles use dual air brake systems. The handbook states plainly that heavy-duty vehicles use dual air brake systems for safety. It then describes how they work: two separate systems sharing one set of brake controls, each with its own tanks, hoses, and lines. Usually one system runs the regular brakes on the rear axle or axles, and the other runs the regular brakes on the front axle. The reason given is safety, since the two systems are separate.
Advertisement
Source
Last checked: 2026-10-17 · Verified from official source
Updated: · Based on the official driver handbook