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Free District of Columbia CDL practice test online

Take a free District of Columbia CDL practice exam online with clear explanations—no sign-up. Coverage includes general knowledge, vehicle systems, combination vehicles, cargo, and endorsements. Then verify current requirements with DC Department of Motor Vehicles.

CDL knowledge tests are federally regulated, so the passing score in District of Columbia is the same as everywhere else: 80% correct on every knowledge test. You must also hold a commercial learner’s permit for 14 days before the skills test.

Start practice Exam-style run

New to the knowledge test? CDL endorsements explained · One-week study plan

Practice coverage
Complete a run to establish your baseline.
600questions
23topics
80%federal pass mark

49 CFR 383.135(a)(1) sets the CDL knowledge-test passing score at 80%. Reaching it here is not a prediction of your official result.

Requirements before you test

District of Columbia CDL test requirements

80%
Passing score
49 CFR 383.135(a)(1)
14 days
CLP held before skills test
49 CFR 383.25(e)
18
Min. age (in-state)
DC Department of Motor Vehicles
21
Min. age (interstate)
49 CFR 391.11(b)(1)

Commercial licensing is largely federal. Any figure above credited to a 49 CFR section applies in every state — see 49 CFR 383.135(a)(1) and 49 CFR 383.25(e). A figure credited to DC Department of Motor Vehicles is District of Columbia’s own, and may be stricter than the federal floor. Test length, fees, and scheduling are set by DC Department of Motor Vehicles (official source).

Entry-Level Driver Training comes first

Since February 7, 2022, a new Class A or Class B CDL, a class upgrade, or a first passenger, school bus, or hazardous materials endorsement requires training from a provider on the FMCSA Training Provider Registry (49 CFR 380.600). Practice questions are study material and do not satisfy that requirement.

FMCSA Training Provider Registry

You need a District of Columbia licence first

A commercial learner’s permit only counts if you already hold an ordinary licence from the same state (49 CFR 383.25(a)(2)). The District of Columbia non-commercial knowledge test runs 30 questions and needs 24 correct, with permits issued from age 16.

District of Columbia permit practice test
Quick practice
10 balanced questions with feedback after every answer.
Practice now
Topic review
Focus on one knowledge area before returning to mixed practice.
See topics
Exam-style run
Answer the full starter bank before seeing your results.
Take the run

What you will practice

Build coverage topic by topic.

Each question carries a topic, difficulty, explanation, and source section so your review has context.

General knowledge29 reviewed questionsMountain driving12 reviewed questionsAir brakes61 reviewed questionsCombination vehicles54 reviewed questionsVehicle systems9 reviewed questionsCargo18 reviewed questionsTank vehicles47 reviewed questionsDoubles and triples43 reviewed questionsHazardous materials71 reviewed questionsSchool bus48 reviewed questionsPassenger vehicles45 reviewed questionsSafe driving6 reviewed questionsSpace management14 reviewed questionsVehicle inspection15 reviewed questionsEmergencies23 reviewed questionsHours of service14 reviewed questionsBasic control11 reviewed questionsSeeing hazards15 reviewed questionsWeather18 reviewed questionsNight driving7 reviewed questionsDriver fitness8 reviewed questionsSpeed management17 reviewed questionsCommunication15 reviewed questions

Sample questions

5 District of Columbia CDL practice questions

Try these District of Columbia sample questions now — each shows the correct answer with a plain-language explanation and a source section. The full 600-question bank is in the practice run.

  1. 1. When loading multi-compartment tanks separated by bulkheads, watch weight distribution so you do not:

    • AGround the vehicle
    • BUse outage
    • Put too much weight on the front or rear of the vehicle
    • DOpen vents

    Answer: Put too much weight on the front or rear of the vehicle. Uneven compartment loading changes handling and can overload axles.

    Source: Commercial Driver License Manual — Tank vehicles — bulkheads

  2. 2. Warn drivers behind of trouble ahead by:

    • AAccelerating suddenly
    • BTurning off all lamps
    • Tapping the brakes lightly to flash brake lights, or using four-ways when driving very slowly if legal
    • DWeaving across lanes

    Answer: Tapping the brakes lightly to flash brake lights, or using four-ways when driving very slowly if legal. Your vehicle’s size can hide hazards from following drivers, so give them early warning.

    Source: Commercial Driver License Manual — Communicating — intentions

  3. 3. When using stab braking on a steep downgrade, you should:

    • Apply brakes fully until wheels lock, release when rolling, and repeat
    • BKeep light, continuous pressure on the pedal at all times
    • CShift to neutral and pump the pedal rapidly
    • DTurn off the engine retarder

    Answer: Apply brakes fully until wheels lock, release when rolling, and repeat. Stab braking involves applying brakes hard until wheels lock, releasing until wheels roll, then re-applying to control speed.

    Source: Commercial Driver License Manual — Driving safely — brake techniques

  4. 4. Compared with a single trailer, triples require:

    • AHigher speeds in curves
    • BLess following distance
    • More room to manoeuvre and greater care in turns
    • DNo change in technique

    Answer: More room to manoeuvre and greater care in turns. Each added trailer increases rearward amplification and off-tracking, so lane changes, turns, and stopping all need more space.

    Source: Commercial Driver License Manual — Doubles and triples — space management

  5. 5. When checking a slack adjuster you can reach, it probably needs adjustment if it moves more than about:

    • 1 inch
    • B3 inches
    • C¼ inch
    • D½ inch

    Answer: 1 inch. Park on level ground, chock wheels, release parking brakes, and pull hard. More than about one inch of free movement at the push-rod attachment usually means adjustment is needed.

    Source: Commercial Driver License Manual — Air brakes — slack adjusters

Practice all 600 questions

CDL knowledge areas

Classes and endorsements, organized.

Each area below scopes the reviewed question bank to one knowledge test. The material is federal, so it applies in District of Columbia just like everywhere else — the endorsement guide explains how the codes fit together.

General knowledge

The foundation for commercial driving: inspections, space, speed, communication, hazards, and safe operation.

  • Pre-trip inspection
  • Space and speed management
  • Railroad crossings
  • Emergency procedures
Practice general knowledge
Air brakes

Understand air-brake components, inspections, warning devices, stopping distance, and controlled braking.

  • Dual air systems
  • Low-air warnings
  • Brake lag and fade
  • Applied-leak and static checks
Practice air brakes
Combination vehicles

Prepare for safe coupling, inspection, turning, backing, and handling of tractor-trailer combinations.

  • Fifth-wheel inspection
  • Coupling and uncoupling
  • Off-tracking
  • Trailer skid prevention
Practice combination vehicles
Hazardous materialsEndorsement H

Study hazard communication, shipping papers, placards, loading rules, parking, and emergency response responsibilities.

  • Hazard classes
  • Placards and labels
  • Shipping papers
  • Loading and segregation
Practice hazardous materials
Tank vehiclesEndorsement N

Learn how liquid surge, outage, bulkheads, and high centers of gravity change vehicle handling.

  • Liquid surge
  • Outage requirements
  • Smooth braking
  • Rollover prevention
Practice tank vehicles
Doubles & triplesEndorsement T

Practice converter-dolly inspection, coupling order, rearward amplification, and stability principles.

  • Coupling sequence
  • Converter dollies
  • Rearward amplification
  • Space management
Practice doubles & triples
Passenger vehiclesEndorsement P

Prepare to inspect, load, and operate buses while keeping passengers, aisles, and exits safe.

  • Vehicle inspection
  • Passenger loading
  • Emergency exits
  • Prohibited practices
Practice passenger vehicles
School busEndorsement S

Review student loading, danger zones, mirrors, emergency procedures, and special railroad-crossing duties.

  • Danger zones
  • Student loading
  • Mirror use
  • Railroad crossings
Practice school bus
Official source hub
Verify current rules before your test.

QuizLane’s starter material points learners back to the agency responsible for licensing in District of Columbia. Rules and manuals can change; the official agency remains authoritative.

Visit DC Department of Motor Vehicles
Our accuracy promise
Original wording—not scraped competitor questions
A source section attached to every reviewed item
A correction path when something looks wrong
Read our methodology

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Common questions

What this practice can—and cannot—tell you.