Delaware DMV CDL General Knowledge Practice Test 3
Test 3 of 5. Pick an answer for each question to see if it is right and why; your score appears at the end. You need 40 correct answers to pass, the same ratio as the real Delaware test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. What happens to a Delaware commercial driver found with a measurable amount of alcohol in his or her system?
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Answer A: The driver is placed out of service for 24 hours
Delaware places out of service for 24 hours any commercial driver who has a measurable amount of alcohol in the system or who refuses an alcohol test.
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2. What is the danger of letting engine speed climb past the top of the rated rpm range before you shift?
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Answer B: You can damage the engine, so the shift should be made before that point
Every engine has a rated operating range; running above it can cause serious engine damage, so the upshift belongs at the top of that range, not beyond it.
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3. Why must tiedowns be rechecked during a trip even when they were tight at the start?
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Answer C: Road vibration and cargo movement can loosen them as the miles go by
Straps and chains settle and loosen as the vehicle bounces and the cargo shifts slightly, so the load must be rechecked at the required intervals.
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4. Around a tractor-trailer, where are the blind areas that other drivers most often sit in unseen?
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Answer A: Along the right side and directly behind the trailer
The blind areas to the right of the cab and behind the trailer are the largest, which is why other drivers should never linger there.
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5. You are making a right turn and cannot complete it without swinging into the oncoming lane. An oncoming car is approaching. What should you do?
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Answer A: Wait and let the oncoming vehicle pass before completing the turn, and do not back up
The oncoming vehicle has the lane; backing up in traffic is dangerous, so hold your position and finish the turn once the way is clear.
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6. Your vehicle stalls on a railroad crossing and a train is coming. What should you do?
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Answer C: Get out at once and move toward the train, well off to one side
Leave the vehicle immediately and move at an angle toward the oncoming train, so that wreckage thrown forward by the impact travels away from you.
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7. A car that passed you on the right slows and stays alongside your trailer. What is the best response?
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Answer D: Ease off the accelerator so the car can move clear
A vehicle sitting beside a trailer is in a blind area and has nowhere to go if you need the lane, so the safest fix is to let it get ahead or behind.
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8. You normally pull an empty trailer, but today the same tractor is loaded to its legal maximum. What changes about getting under way?
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Answer A: You may need to start in a lower gear, since the load takes more pulling power
The heavier the load, the lower the gear needed to get the vehicle rolling without lugging or stalling the engine.
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9. Where should a trailer be dropped, and what else does the driver do before pulling out from under it?
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Answer C: On solid level ground, with the trailer wheels chocked if it may roll
A dropped trailer must sit on ground that will carry the landing gear without sinking, and chocks stop it rolling once the tractor and its air supply are gone.
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10. You drop your phone on the floor of the cab while driving. What do federal rules require?
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Answer A: Leave it, because reaching for it while driving is banned
Federal rules forbid reaching for a mobile device in any way that takes the driver out of a seated, belted driving position.
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11. On the Interstate System, what is the federal maximum weight allowed on a single axle?
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Answer A: 20,000 pounds
Federal limits for the Interstate System cap one single axle at 20,000 pounds.
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12. A commercial driver is convicted of two serious traffic violations within three years. What is the result?
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Answer D: Disqualification for 60 days
Two serious traffic violations in a three year period bring a 60 day disqualification, and a third in the same period raises it to 120 days.
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13. What does the gross vehicle weight rating of a vehicle describe?
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Answer A: The maximum loaded weight of that single vehicle, as specified by the manufacturer
The rating is the manufacturer figure for the loaded weight of one vehicle, so it is a limit fixed in advance rather than a measurement of the load on board today.
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14. At 55 mph on dry pavement with good brakes, total stopping distance for a loaded heavy vehicle is roughly what?
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Answer B: About 400 feet or more
Perception, reaction, and braking together add up to roughly 400 feet or more, farther than the length of a football field.
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15. You are stopped in a line of traffic behind a car. How much space should you leave in front of you?
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Answer C: Enough to see where the rear tires of that car meet the road
That amount of space lets you pull around the vehicle ahead if it stalls and absorbs some of the shock if you are struck from behind.
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16. What is the consequence in Delaware of two or more convictions for listed major commercial driving offenses arising from separate incidents?
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Answer A: Lifetime disqualification
Two or more convictions for the listed offenses from separate incidents result in lifetime disqualification.
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17. Why should a driver avoid shifting gears in the middle of a turn at an intersection?
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Answer D: Shifting during the turn takes a hand off the wheel and can cost you control
Pick the gear before you begin turning; shifting in the turn removes a hand from the wheel and can interrupt power just when you need steady control.
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18. What are you checking when you look at the batteries during the engine compartment inspection?
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Answer D: That they are securely mounted, the connections are tight and free of corrosion, and the caps are in place
Loose or corroded batteries can fail or short out, so the mount, cables, terminals and vent caps are all part of the check.
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19. Why should a long vehicle never swing out to the left before starting a right turn?
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Answer D: Another driver may read it as a left turn or pass on your right
Swinging left opens a gap on your right that a car will move into, and it also sends a false message about which way you are going.
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20. An article of cargo has been blocked so that it cannot move forward. How many tiedowns does the federal rule call for?
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Answer A: One tiedown for every 10 feet of article length, or any part of that
Blocking against forward movement lowers the requirement to one tiedown per 10 feet of length or fraction of 10 feet.
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21. The combined working load limit of the tiedowns on a load must equal at least what share of the cargo weight?
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Answer C: One half of the cargo weight
Federal securement rules set the aggregate working load limit at no less than half the weight of the article or group of articles being held.
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22. Which document must be available to show that the annual inspection was carried out?
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Answer C: The inspection report or a copy of it, or a decal displayed on the vehicle
Proof of the periodic inspection travels with the vehicle, either as the report itself or as the decal fixed where an inspector can see it.
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23. Who may remove an out-of-service sticker from a commercial vehicle?
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Answer B: Only an authorized person, and only after the defect that caused it has been repaired
The sticker stays on the vehicle until the repairs are made and an authorized person removes it, so nobody can simply peel it off and drive away.
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24. A sign before a long descent shows 6 percent. What does that number tell you?
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Answer A: How steep the grade ahead is
Percent grade is the drop in feet for every hundred feet of road, so the higher the number the faster speed will build and the lower the gear you need.
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25. How are the extra gears of a multi-speed rear axle or auxiliary transmission usually controlled?
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Answer D: With a selector knob or switch on the gearshift lever of the main transmission
A range selector on the shift lever lets the driver choose the extra gear range while shifting the main transmission.
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26. Why does a cracked frame rail or cross member make a vehicle unsafe?
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Answer B: The frame carries the whole load, and a crack can spread until the structure fails
The frame is the backbone that supports the body, the load and the running gear, so a crack in it is a structural failure that grows with every mile.
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27. A roadside test shows a commercial driver has measurable alcohol in the system but below 0.04. What happens?
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Answer C: The driver is placed out of service for 24 hours
Any measurable alcohol while on duty results in an immediate 24 hour out of service order, even when the concentration is under the 0.04 limit.
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28. What is the minimum tread depth required in every major groove of a steering axle tire?
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Answer D: 4/32 inch
Federal rules set a higher tread minimum for front steering tires than for other positions because a steering tire failure is far harder to control.
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29. What is the basic rule about backing a large vehicle?
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Answer B: Avoid backing whenever there is another way
Backing is dangerous because you cannot see everything behind you, so the manual tells drivers to plan routes and parking that avoid it.
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30. Under the federal hours of service rules, when must a property-carrying driver take a 30 minute break?
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Answer C: After 8 cumulative hours of driving time
Driving is not allowed after 8 cumulative hours of driving time without at least a 30 consecutive minute interruption of driving.
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31. How long must a Delaware commercial learner's permit be held before the CDL skills test may be taken?
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Answer B: Fourteen days
Delaware schedules CDL skills tests only after the applicant has held the commercial learner's permit for at least 14 days.
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32. During the walkaround inspection, where does the driver normally start and how does the check proceed?
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Answer C: At the left front of the vehicle, working around it in a set order that returns to the cab
The walkaround follows the same route every time, starting at the left front and circling the vehicle, so that nothing is skipped when the driver is tired or rushed.
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33. Which parts of total stopping distance can a driver shorten simply by staying alert and looking far ahead?
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Answer B: Perception distance and reaction distance
Alertness shortens the time spent recognizing a hazard and moving your foot to the pedal; braking distance depends on speed, weight, brakes and the road surface.
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34. You are on a freeway and see brake lights come on in several vehicles far ahead of you. What should you do?
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Answer A: Ease off the accelerator and get ready to slow down
Brake lights well ahead are an early warning that traffic is slowing, and acting on them gives a heavy vehicle the room it needs.
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35. You must drive well below the speed of surrounding traffic, for example when climbing a steep grade with a heavy load. What should you do?
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Answer B: Turn on the four-way flashers to warn following traffic, where state law allows it
Flashers warn faster traffic that a slow-moving vehicle is ahead, which helps prevent rear-end crashes; some states restrict their use while moving, so check the local rule.
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36. What color must the clearance and side marker lamps and reflectors at the front of a trailer be?
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Answer A: Amber
Amber marks the front and the forward part of the sides of a vehicle, while red marks the rear, so another driver can tell which way the vehicle is facing.
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37. What is a bulkhead in a cargo body used for?
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Answer D: To divide the space and stop cargo from moving into another part of the body
A bulkhead is a solid partition that separates one part of the load space from another and blocks the cargo from moving past it.
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38. On the Interstate System, what are the federal maximums for a tandem axle group and for gross vehicle weight?
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Answer B: 34,000 pounds and 80,000 pounds
The federal Interstate limits allow 34,000 pounds on a tandem axle group and 80,000 pounds gross.
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39. Federal rules require a power unit that is not carrying placarded hazardous materials to have a fire extinguisher with which minimum rating?
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Answer A: One rated 5 B:C or more, or two rated 4 B:C or more each
The minimum is a single unit rated 5 B:C or more, or two units of at least 4 B:C each, which is enough to attack a fuel or electrical fire.
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40. Why is a leaking exhaust system on a commercial vehicle dangerous to the driver?
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Answer B: It can let carbon monoxide reach the cab, where it can poison the occupants
Exhaust gas contains carbon monoxide, which has no smell and dulls the driver judgment long before it becomes obvious that anything is wrong.
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41. Federal rules keep recapped and retreaded tires off the front wheels of which vehicle?
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Answer B: Any bus carrying passengers
The federal rule names buses: a bus may not run with regrooved, recapped or retreaded tires on its front wheels, because a steer tire failure with passengers aboard takes away steering control.
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42. When turning left, what should a driver of a long vehicle do before beginning the turn?
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Answer B: Reach the center of the intersection so the rear wheels clear the corner
The rear wheels follow a tighter path than the front, so the vehicle must reach the center of the intersection before the turn begins.
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43. How do you get more engine braking from an automatic transmission on a downgrade?
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Answer B: Select a lower range before starting down
Locking the transmission into a lower range keeps engine speed high enough to hold the vehicle back and spares the service brakes.
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44. What must be true of the trailer landing gear before you move off?
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Answer B: Fully raised, with the crank handle secured and no missing or damaged parts
Landing gear left part way down can strike a railway crossing or a ramp, and a loose crank handle can swing out into a passing vehicle.
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45. You miss a gear while double clutching and the transmission is stuck in neutral. What should you do?
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Answer B: Return to neutral, release the clutch, bring engine speed to match road speed and try again
Forcing the lever damages the gears; matching the engine speed to the road speed lets the gear engage cleanly on the next try.
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46. Why should a large vehicle be accelerated smoothly and gradually?
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Answer A: Rough acceleration can damage the drivetrain and, on a combination, the coupling
Jerky throttle inputs put shock loads through the driveline and the coupling, which causes mechanical damage over time.
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47. Why must you never coast down a hill in neutral or with the clutch pushed in?
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Answer C: You lose the braking effect of the engine and your brakes may overheat and fail
Engine braking is what keeps a heavy vehicle in check on a grade; coasting throws it away and leaves the service brakes to do all the work until they overheat.
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48. What is checked about the engine cooling system during the engine compartment inspection?
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Answer C: That the coolant level is adequate and the radiator and hoses are not leaking
A low coolant level or a leaking hose leads to overheating, which can stop the vehicle in a place where stopping is dangerous.
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49. You are about to back across a quiet street into a driveway. Which of these is good practice before you start to move?
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Answer B: Turn on the four-way flashers and sound the horn to alert anyone nearby
Warning other road users and pedestrians before a reverse maneuver gives them the chance to stop or move clear before the vehicle starts back.
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50. A brake light lens is cracked and the lamp still lights. How should that be treated?
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Answer B: As a defect, because water can enter and the lamp can dim or fail
A cracked lens lets in water and dirt, which corrodes the socket and dulls the lamp, so it is reported before it becomes a dead brake light.