DC · GK Endorsement

District of Columbia General Knowledge CDL Practice Test

Below are 25 exam-style questions for the District of Columbia General Knowledge CDL knowledge test, modeled on the FMCSA-aligned content used by the DC Department of Motor Vehicles. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.

Question 1 of 25

When backing a heavy vehicle, you should:

A Back fast to get it over with
B Use a helper and walk around the vehicle first
C Back without using mirrors so you can watch out the window
D Back to the right whenever possible

Correct answer: B

Always GOAL — Get Out And Look — and use a helper. Backing to the left when possible is preferred because you can see better, not to the right.

Question 2 of 25

The two main reasons why a driver's feet are kept off the brakes when not actively braking are:

A To save brake pads and reduce drag
B So the brake lights don't mislead following drivers and so the brakes don't overheat
C To rest the right leg
D To save fuel and improve mileage

Correct answer: B

Riding the brake lights confuses drivers behind you and gradually heats the friction surfaces, both of which are safety problems.

Question 3 of 25

The maximum allowable on-duty driving time after 8 consecutive hours off duty is:

A 10 hours
B 11 hours
C 16 hours
D 14 hours

Correct answer: B

After 10 hours off duty, a property-carrying driver may drive up to 11 hours, within a 14-hour on-duty window.

Question 4 of 25

Drivers may not drive after being on duty:

A 15 hours of driving
B 20 hours in a 24-hour period
C 8 hours in any 24-hour period
D 14 consecutive hours since coming on duty

Correct answer: D

The 14-hour rule limits the on-duty window during which up to 11 hours of driving may occur.

Question 5 of 25

Which is true about driving in fog?

A Use low-beam headlights and slow down
B Drive faster to get out of the fog quickly
C Use the four-ways while in motion at highway speed
D Use high-beam headlights for maximum visibility

Correct answer: A

High beams reflect off fog and reduce visibility. Slow down and use low beams or fog lamps if equipped.

Question 6 of 25

A driver must report any accident involving a CMV to the carrier within:

A 24 hours
B A reasonable time, before going off duty
C 7 days
D 1 hour

Correct answer: B

FMCSA rules require notification of the motor carrier in a reasonable time — most policies treat that as before going off duty.

Question 7 of 25

When driving at night, you should adjust speed so that you can stop within:

A Whatever speed feels safe
B The range of your low-beam headlights
C The full range of high-beam headlights when in use
D Half the range of your low-beam headlights

Correct answer: B

Always be able to stop within the distance you can see. At night with low beams, that's typically about 250 feet.

Question 8 of 25

Which is true about driving in rain?

A Roads are most slippery just after rain begins, when water mixes with road oil
B Tire chains are required by federal law
C It is safe to drive at the posted speed limit
D High beams improve visibility in heavy rain

Correct answer: A

The first few minutes of rain mix with oil and grime on the road and create the slipperiest conditions. Slow down and increase following distance.

Question 9 of 25

Cargo that hangs more than 4 feet beyond the back of the vehicle must be marked with:

A A green flag
B A red flag (or red light at night) at the extreme rear
C Nothing — federal rules do not require marking
D Yellow tape only

Correct answer: B

Federal rules require a red flag during the day and red lights at night for projecting cargo beyond 4 feet.

Question 10 of 25

You are driving on a two-lane road and you see a driver about to pull out from a side road. You should:

A Cover the brake and slow down
B Move to the right lane
C Honk and accelerate
D Maintain speed

Correct answer: A

Anticipate the worst-case behavior. Cover the brake — keeping your foot just over it — so you can react if they pull out.

Question 11 of 25

When should you do an en-route inspection?

A Only if a warning light comes on
B Within the first 25 miles, then about every 150 miles or every 3 hours
C Only when the load is hazardous
D At the end of the trip

Correct answer: B

The FMCSA model manual recommends a check within the first 25 miles to catch loose cargo or under-inflated tires that have warmed up, then about every 150 miles or 3 hours, and any time you stop.

Question 12 of 25

A driver who has lost the ability to safely brake the vehicle on a downgrade should:

A Look for an escape ramp
B Use the parking brake hard
C Coast in neutral
D Shift into reverse

Correct answer: A

Long downgrades have escape ramps for runaway trucks. Use them. Coasting in neutral is illegal in many states and worsens the problem.

Question 13 of 25

A controlled braking technique means:

A Coasting in neutral
B Locking the wheels
C Pumping the brakes hard and fast
D Applying the brakes as hard as possible without locking the wheels

Correct answer: D

Controlled braking applies brakes hard but stops short of wheel lock-up. With ABS, you can simply press and hold full pressure.

Question 14 of 25

When approaching a railroad crossing in a CMV that is not required to stop, you should:

A Slow down, look, listen, and be prepared to stop
B Honk and proceed
C Cross at maximum speed to get over quickly
D Always come to a full stop regardless of traffic

Correct answer: A

Even when not required by class to stop, you must always be prepared to stop. Buses, hazmat, and certain other vehicles must stop every time.

Question 15 of 25

Which of the following is NOT part of a pre-trip inspection?

A Checking the engine compartment
B Walking around the vehicle and checking lights
C Testing the service and parking brakes
D Adjusting the trailer brakes individually

Correct answer: D

Adjusting brakes is a maintenance task done by qualified personnel, not a pre-trip step. The driver checks for proper operation, not adjustment.

Question 16 of 25

A driver convicted of a major offense (DUI, leaving the scene, etc.) in a CMV faces:

A No federal consequence
B A warning
C A fine only
D CDL disqualification for at least one year for a first offense

Correct answer: D

Major offenses carry a one-year CDL disqualification minimum (three years if hauling hazardous materials), and lifetime for a second.

Question 17 of 25

Which is true about driving in mountains?

A Engine braking helps keep speed under control
B Brakes alone are not designed to hold a heavy vehicle on a long downgrade
C Heavy vehicles can slow down sharply on grades
D All of the above

Correct answer: D

Mountain driving combines all three. Use of low gears, engine braking, and short, moderate service-brake applications is the safe combination.

Question 18 of 25

Which of the following is a sign of fatigue?

A Drifting in your lane
B Trouble remembering the last few miles
C Frequent yawning
D All of the above

Correct answer: D

All three are classic fatigue indicators in the FMCSA model. Cold air, music, and caffeine are not effective fixes — only sleep is.

Question 19 of 25

What is the most important reason for doing a vehicle inspection?

A To meet your dispatcher's schedule
B To reduce tire wear
C To improve fuel economy
D Safety for yourself and other road users

Correct answer: D

Federal rules and the FMCSA model manual list safety as the single most important reason for a pre-trip inspection. Mechanical defects discovered before the trip cannot kill anyone on the highway.

Question 20 of 25

Hours-of-service records are required to be kept by:

A The driver, in the form of a logbook or electronic logging device
B The dispatcher only
C The carrier only
D No one

Correct answer: A

Drivers are responsible for accurate hours-of-service records, kept either on paper logs or, for most carriers, on an ELD.

Question 21 of 25

A leaking exhaust system is dangerous because:

A It is illegal
B It can let poisonous carbon monoxide into the cab
C It increases fuel use
D It causes the engine to overheat

Correct answer: B

Carbon monoxide from a leaking exhaust can cause headaches, drowsiness, and unconsciousness. The illegality is real but the safety risk is the bigger answer.

Question 22 of 25

When approaching a steep downgrade, the basic safe-driving rule is:

A Coast in neutral
B Select a lower gear before starting down
C Stay in high gear
D Use the parking brake intermittently

Correct answer: B

Get into a low gear before the descent so the engine helps hold the vehicle back.

Question 23 of 25

On a long downgrade, why is it dangerous to use the brakes too much?

A It wastes brake pads
B It triggers the ABS warning light
C It cools the brakes too much
D Brake fade can leave you with reduced or no braking power

Correct answer: D

Heat from continuous braking causes the friction surfaces to lose their grip. Use a low gear and brief, moderate brake applications.

Question 24 of 25

When the road is slippery, you should:

A Make smooth steering and braking inputs
B Increase following distance
C Slow down
D All of the above

Correct answer: D

Slippery roads require all three: more cushion, smoother inputs, and lower speed.

Question 25 of 25

A CDL is required to operate a single vehicle with a GVWR of:

A 10,001 lbs or more
B 40,000 lbs or more
C 26,001 lbs or more
D 20,000 lbs or more

Correct answer: C

Single vehicles at or above 26,001 lbs GVWR (Class B) require a CDL. Class A applies to combinations at or above 26,001 lbs GCWR with a trailer over 10,000 lbs.

Study tips for the District of Columbia General Knowledge exam

The General Knowledge portion of the District of Columbia CDL exam is graded out of the bank of questions the DC Department of Motor Vehicles draws from each year. While the exact bank is not published, every question is sourced from the General Knowledge chapter of the District of Columbia CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official District of Columbia handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about General Knowledge.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The DC Department of Motor Vehicles will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the General Knowledge exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh District of Columbia General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the General Knowledge study guide and the matching chapter in the official District of Columbia CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local DC Department of Motor Vehicles office.

Already comfortable with this endorsement? Drill another: DC Air Brakes · DC Combination Vehicles · DC Hazardous Materials · DC Passenger · DC School Bus · DC Tank Vehicle · DC Doubles / Triples

New to the CDL process in District of Columbia? Read How to apply for a CDL in District of Columbia for the document checklist and step-by-step timeline.