District of Columbia General Knowledge CDL Practice Test

This is a free 20-question practice test for the General Knowledge portion of the District of Columbia Commercial Driver's License knowledge exam. Questions are pulled from a pool of 97 drawn from the AAMVA CDL Manual, which is the source document the District of Columbia Department of Motor Vehicles uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in District of Columbia.

Question 1 of 20

Which of the following is NOT part of the seven-step pre-trip inspection method?

Approach the vehicle and overview
Check the engine compartment
Test the AM/FM radio
Walk around inspection

Correct. The radio is not part of the safety inspection. The seven-step method covers approach, engine compartment, in-cab checks, lights, walk-around, signal lights, and brake checks.

Question 2 of 20

You are driving on a two-lane road. An oncoming driver drifts into your lane. You should:

Steer right onto the shoulder
Flash your high beams
Honk your horn
Brake hard and stop in your lane

Correct. When an oncoming driver drifts into your lane, the safer escape is right onto the shoulder. Steering left risks a head-on if the other driver corrects.

Question 3 of 20

Which lane is generally the best for a commercial vehicle on a multi-lane highway?

The far left (passing) lane
The middle lane
The right lane (slow lane)
Whichever has the lightest traffic

Correct. The right lane is generally best — it limits lane changes, reduces conflict with merging traffic only on the right, and matches commercial-vehicle speed.

Question 4 of 20

What does it mean when a driver is "hydroplaning"?

The truck is overheating
The tires lose contact with the road and ride on a film of water
The brakes have failed
The driver is dehydrated

Correct. Hydroplaning means tires have lost contact with the pavement and are riding on standing water. Steering and braking become ineffective.

Question 5 of 20

When you double your speed from 20 to 40 mph, the impact in a crash is:

Twice as great
Three times as great
Four times as great
The same

Correct. Crash energy is proportional to the square of speed. Doubling speed quadruples the energy of impact.

Question 6 of 20

When approaching a curve, you should:

Brake during the curve
Slow down before the curve, then accelerate gently through it
Maintain steady speed
Speed up to maintain control

Correct. Slow before entering the curve. Once in the curve, accelerate gently to maintain stability — braking in a curve invites a skid or rollover.

Question 7 of 20

Cargo securement is the responsibility of:

Only the shipper
Only the consignee
The driver, regardless of who loaded the trailer
The dispatcher

Correct. The driver is ultimately responsible for verifying that cargo is properly secured before driving and remains secure throughout the trip.

Question 8 of 20

How often must drivers inspect their cargo and securing devices?

Within the first 50 miles, then every 150 miles or every 3 hours of driving (whichever comes first)
Only at the start of the trip
Only at fuel stops
Only when entering a new state

Correct. Federal rule: inspect within the first 50 miles, then every 150 miles or 3 hours of driving, whichever comes first, plus every change of duty status.

Question 9 of 20

You are driving a 40-foot vehicle at 35 mph. The minimum following distance you should maintain is:

2 seconds
3 seconds
4 seconds
7 seconds

Correct. The rule of thumb: 1 second per 10 feet of vehicle length below 40 mph. A 40-foot vehicle therefore needs 4 seconds of following distance.

Question 10 of 20

Which of the following is true about driving at night?

Headlights illuminate further than you can stop within
You should drive faster to keep up with traffic
You should drive at a speed that lets you stop within the distance illuminated by your headlights
You can rely on oncoming headlights to help you see

Correct. Drive at a speed where your stopping distance does not exceed the distance you can see — typically 250 feet on low beams, 350-500 feet on high beams.

Question 11 of 20

The four-way flashers on a commercial vehicle should be used:

Anytime you are stopped or moving slowly enough that other drivers might not expect
Only when parked
Only at night
Only on the interstate

Correct. Use four-way flashers anytime your vehicle is stopped on or near the roadway, or moving slowly enough that approaching traffic might be surprised.

Question 12 of 20

A tire may need replacement if:

Tread depth is below the minimum (4/32 steer, 2/32 other), there are sidewall cuts, exposed cord, or other damage
It looks dirty
It is over a year old
It is the wrong color

Correct. Below-minimum tread depth, sidewall damage, exposed cords, bulges, or excessive wear are all reasons to replace.

Question 13 of 20

A driver should look down the road how far when driving at highway speeds?

One block
One-quarter mile (about 12-15 seconds ahead)
Just past the hood
To the horizon only

Correct. Look 12-15 seconds ahead — about a quarter mile at highway speeds. This gives time to identify and react to hazards.

Question 14 of 20

If your vehicle hydroplanes, what should you do?

Brake hard immediately
Steer sharply to recover
Release the accelerator and push in the clutch
Accelerate to push through

Correct. Release the accelerator and push in the clutch. Do not brake or steer hard until the tires regain contact.

Question 15 of 20

You are driving on a steep downgrade and your brakes have failed. The best escape is to:

Pump the brakes furiously
Use a runaway escape ramp
Try to bail out of the cab
Sound the horn and continue

Correct. If a runaway escape ramp is available, use it. Modern arrester beds use loose gravel or sand to slow the vehicle without injury to the driver.

Question 16 of 20

Convex (curved or "fish-eye") mirrors:

Show objects larger than they appear
Show a wider area but make objects look smaller and farther away than they actually are
Are not legal on commercial vehicles
Cannot be used at night

Correct. Convex mirrors widen the field of view but distort distance — objects appear smaller and farther away than they are.

Question 17 of 20

When a vehicle ahead of you brakes hard, you should:

Brake harder
Apply the brakes immediately, even if you don't need to
Look for a way to steer around the vehicle if necessary, while preparing to brake
Honk to warn the driver behind you

Correct. Plan your escape: identify a clear lane or shoulder. If you can steer to safety, you save reaction time. If not, brake firmly without locking the wheels.

Question 18 of 20

Maximum allowable steering-wheel play is approximately:

5 degrees
10 degrees
20 degrees
30 degrees

Correct. Steering wheel play should not exceed 10 degrees (roughly 2 inches on a 20-inch wheel). More than that, the vehicle is hard to steer.

Question 19 of 20

Hazardous materials awareness is required for:

Only Hazmat-endorsed drivers
Every CDL holder, even without an H endorsement
Only owners
Only mechanics

Correct. Every CDL applicant must understand basic hazmat awareness — recognizing placards, labels, and shipping papers — even if they never haul hazmat.

Question 20 of 20

On a vehicle equipped with ABS, you should:

Pump the brakes during emergency stops
Apply the brakes the way you always have, with steady pressure
Use the parking brake instead
Never use the service brakes

Correct. With ABS, brake the way you always would. The system prevents wheel lockup automatically; pumping interrupts ABS function.

About the District of Columbia General Knowledge exam

Most state DMVs administer 50 General Knowledge questions and require 80% (40 correct) to pass. Questions are pulled from a much larger pool, so two applicants taking the test on the same day will see different mixes. The questions on this site are drawn from the AAMVA CDL Manual chapters that every state's exam is built from.

The District of Columbia Department of Motor Vehicles follows the federal CDL standards established by FMCSA. To earn the General Knowledge credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full General Knowledge question bank or browse all District of Columbia CDL practice tests.