A low-air pressure warning device that drops a flag in front of the driver

DE · GK Endorsement

Delaware General Knowledge CDL Practice Test

Below are 25 exam-style questions for the Delaware General Knowledge CDL knowledge test, modeled on the FMCSA-aligned content used by the Delaware Division 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 driving at night, you should adjust speed so that you can stop within:

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

Correct answer: D

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

Question 2 of 25

A leaking exhaust system is dangerous because:

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

Correct answer: D

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 3 of 25

Stab braking is used:

A On vehicles with ABS
B To save fuel
C On vehicles without ABS, to keep them straight in an emergency
D On wet roads only

Correct answer: C

Stab braking — full application then release as soon as wheels lock, then re-apply — is for non-ABS vehicles. With ABS, do not pump.

Question 4 of 25

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

A A warning
B A fine only
C No federal consequence
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 5 of 25

Stopping distance is made up of:

A Speed times weight
B Perception distance + reaction distance + brake-lag distance + braking distance
C Reaction distance only
D Brake-lag distance only

Correct answer: B

Total stopping distance has four parts. Air brakes add a brake-lag distance not present in hydraulic systems.

Question 6 of 25

A "wig-wag" is:

A A low-air pressure warning device that drops a flag in front of the driver
B A type of cargo strap
C A trailer hitch component
D A fuel-saving switch

Correct answer: A

On older trucks, a wig-wag is a mechanical low-air warning that lowers a flag into the driver's field of view when air pressure drops below safe limits.

Question 7 of 25

When should you do an en-route inspection?

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

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 8 of 25

Black ice is most likely on:

A Gravel surfaces
B Bridges and overpasses
C Roads in direct sunlight
D Concrete pavement only

Correct answer: B

Bridges and overpasses freeze first because cold air circulates above and below them. They are the most-asked test scenario for sudden ice.

Question 9 of 25

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

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

Correct answer: D

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

Question 10 of 25

Drivers may not drive after being on duty:

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

Correct answer: B

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

Question 11 of 25

The most important hand position on the steering wheel is:

A One hand at 12
B Both hands at the bottom
C 12 and 6
D 10 and 2 (or 9 and 3)

Correct answer: D

A balanced grip at 10-and-2 or 9-and-3 gives the most control. One-handed and bottom-of-wheel positions reduce reaction time.

Question 12 of 25

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

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

Correct answer: B

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 13 of 25

When you are being tailgated, you should:

A Speed up to get away
B Move to the left lane only
C Increase your following distance from the vehicle in front to give both of you more room
D Brake suddenly to teach a lesson

Correct answer: C

Adding cushion ahead gives the tailgater room to pass safely and reduces the chance of a chain rear-end collision.

Question 14 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 Move to the right lane
B Cover the brake and slow down
C Maintain speed
D Honk and accelerate

Correct answer: B

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

Question 15 of 25

When the road is slippery, you should:

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

Correct answer: B

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

Question 16 of 25

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

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

Correct answer: B

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

Question 17 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 Always come to a full stop regardless of traffic
C Cross at maximum speed to get over quickly
D Honk and proceed

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 18 of 25

The proper response to a tire blowout on the front axle is to:

A Steer sharply toward the shoulder
B Shift to neutral and coast
C Hold the steering wheel firmly, ease off the accelerator, and let the vehicle slow down
D Brake immediately and pull off the road

Correct answer: C

Hard braking after a blowout can cause loss of control. Hold the wheel, release the accelerator, and let speed bleed off before braking gently.

Question 19 of 25

You may not drive a CMV with a blood-alcohol concentration of:

A Any detectable amount above 0.00%
B 0.04% or higher
C 0.08% or higher
D 0.10% or higher

Correct answer: B

0.04% is the regulatory limit for CMV operation. A detectable amount under that triggers an out-of-service order but is not necessarily a DUI conviction.

Question 20 of 25

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

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

Correct answer: A

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

Question 21 of 25

Hydroplaning is most likely when:

A Tires are over-inflated
B Tires lose contact with the road on a film of water
C Roads are dry but hot
D You brake hard on dry pavement

Correct answer: B

Hydroplaning happens when tires ride on top of standing water at speed. Reduce risk by slowing down, keeping tires properly inflated and tread depth adequate.

Question 22 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 To rest the right leg
C So the brake lights don't mislead following drivers and so the brakes don't overheat
D To save fuel and improve mileage

Correct answer: C

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

Question 23 of 25

The minimum tread depth for steer-axle tires is:

A 4/32 inch
B 2/32 inch
C 1/32 inch
D 6/32 inch

Correct answer: A

Steer tires must have at least 4/32 inch in every major groove. Other tires require at least 2/32 inch.

Question 24 of 25

Which is true about driving in rain?

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

Correct answer: C

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 25 of 25

How does ABS help in an emergency stop?

A It increases brake pressure automatically
B It applies the parking brake
C It always stops the vehicle in a shorter distance
D It prevents wheel lockup so the driver can keep steering

Correct answer: D

ABS keeps the wheels rolling so steering control is preserved. It is not a shorter-distance device.

Study tips for the Delaware General Knowledge exam

The General Knowledge portion of the Delaware CDL exam is graded out of the bank of questions the Delaware Division 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 Delaware 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 Delaware 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 Delaware Division 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 Delaware 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 Delaware 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 Delaware Division of Motor Vehicles office.

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

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