California DMV CDL General Knowledge Practice Test 1
Test 1 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 California test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. You pick up a trailer that another driver dropped in the yard. What must you do before pulling it?
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Answer B: Inspect it yourself, because you are responsible for the whole vehicle you drive
Responsibility follows the driver who moves the vehicle, and a trailer that has stood in a yard may have lost air, developed a flat tire or been damaged.
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2. Which winter preparation matters most for keeping the road in view?
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Answer D: Working wipers, washer fluid and a working defroster
Slush and road spray coat the windshield within minutes in winter, so wipers, washer fluid and the defroster are what keep any view at all.
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3. Besides being uncomfortable, what can a series of hard, jerky brake applications do to a loaded combination?
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Answer A: Shift the load and push the trailer out of line behind the tractor
Sudden, uneven braking can move cargo forward and upset the alignment of a trailer, which is why stops should be made smoothly.
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4. Below 40 mph, what following distance does the standard commercial rule of thumb call for?
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Answer C: One second for every 10 feet of vehicle length
The base rule allows one second of space for each 10 feet of vehicle length while speed stays under 40 mph.
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5. You are pulling a loaded pneumatic dry bulk trailer and approach an exit ramp posted at 35 mph. What is the safest approach?
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Answer C: Slow to well below the posted speed before the ramp begins
A dry bulk trailer carries its weight high and the load can move, so the ramp speed posted for a car is far too fast and the slowing must be finished before the curve.
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6. You are entering a freeway from a short ramp with a fully loaded trailer. What should you do?
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Answer A: Begin building speed early and wait for a large gap
A loaded vehicle accelerates slowly, so it needs both a running start and a much larger gap than a car would use.
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7. Which items belong to the in-cab part of the inspection?
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Answer D: Gauges, controls, mirrors, windshield, wipers, horn, heater and defroster
The in-cab step checks the instruments and controls the driver depends on, along with mirrors, glass, wipers, horn and the heater and defroster.
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8. An enforcement officer inspects your vehicle at the roadside and attaches an out-of-service sticker. What may you do?
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Answer C: Nothing until the defect is repaired; the vehicle may not be driven
An out-of-service order means the vehicle is unsafe, and no schedule, load or destination allows it to be driven before the defect is corrected.
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9. How are the headlights, marker lights and turn signals checked during the seven-step inspection?
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Answer A: The engine is shut off, the parking brake is set, the lights are switched on and then checked from outside the vehicle
The lights are switched on with the vehicle secured, then the driver walks around and confirms each lamp actually works and is clean.
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10. At the scale your tractor drive axles are overweight while the trailer axles have room. Sliding the trailer tandems forward will do what?
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Answer C: Move weight off the drive axles and onto the trailer axles
Sliding the trailer tandems forward brings the rear support closer to the load, so the trailer axles pick up more weight and the drive axles carry less; sliding them rearward does the opposite.
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11. An intermodal container is being carried on an ordinary flatbed rather than on a container chassis. What does that mean for securement?
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Answer B: It must be secured with tiedowns that meet the container securement requirements
A container carried on a vehicle that is not fitted with integral locking devices has to be secured to the deck with tiedowns that satisfy the rules for containers.
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12. Using the snub braking method on a downgrade, when does the driver release the brakes?
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Answer A: After speed has dropped about 5 mph below the safe speed
The driver brakes firmly to about 5 mph under the chosen safe speed, releases to let the brakes cool, then repeats when the safe speed returns.
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13. Why should high beams not be used in fog?
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Answer A: The light reflects back off the droplets and blinds you
Fog is made of water droplets that scatter light straight back at the driver, so a stronger beam makes the wall of glare worse rather than better.
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14. Which shock absorber condition is a defect?
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Answer C: A shock that is leaking, broken or disconnected at either mounting
A shock that has lost its fluid or its mounting no longer damps the suspension, so the wheel bounces and loses contact with the road.
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15. 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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16. Why does the commercial driver manual tell you to look far down the road instead of only at the vehicle ahead?
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Answer D: So you can adjust smoothly instead of braking hard at the last moment
A heavy vehicle cannot react quickly, so early information lets you slow gradually rather than make a sudden stop or swerve.
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17. Why must the driver of a large vehicle keep it centered in its lane?
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Answer B: The vehicle needs the full width of the lane
A commercial vehicle is close to lane width already, so any drift takes part of the vehicle into the next lane or onto the shoulder.
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18. You are inspecting the vehicle alone and need to confirm that the stop lights work. Which method is correct?
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Answer A: Have a helper press the brake pedal, or apply the brake in a way that keeps it on while you check from outside
Stop lights are checked from outside the vehicle while the brakes are applied, so a helper or a brake held on is needed.
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19. What is the minimum age to apply for a California commercial learner's permit or commercial driver license?
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Answer D: 18 years old
California requires applicants to be at least 18 years old for a commercial learner's permit or commercial driver license, and the applicant must already hold a California noncommercial Class C license.
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20. What is the driver looking for when the exhaust system is inspected?
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Answer B: Loose, broken or missing pipes, brackets or clamps, and signs that exhaust is leaking
A loose or leaking exhaust system can send carbon monoxide into the cab and can put hot gas against parts that will burn.
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21. The only way into a customer yard forces you to back toward the right, or blind, side of the vehicle. What should you do?
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Answer D: Use a helper and get out to check the path more often than you normally would
Blind side backing is allowed but far riskier, so it calls for a spotter you can see and for repeated checks of the path on foot.
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22. What should you look for on the electrical wiring in the engine compartment?
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Answer A: Worn, frayed or cracked insulation and loose or corroded connections
Damaged insulation can short a circuit against the frame or engine, which can kill a lamp you depend on or start a fire.
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23. Where must a California school bus carrying pupils stop at a railroad crossing?
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Answer D: Between 15 and 50 feet from the nearest rail of the track
Section 22452 requires the driver to stop not less than 15 nor more than 50 feet from the nearest rail, then listen and look both ways along the track.
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24. Part of looking well ahead is planning an out. What does that mean?
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Answer B: Keeping an escape path in mind in case traffic stops suddenly
Because a heavy vehicle often cannot stop in time, good drivers continuously note where they could steer if the space ahead closes.
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25. Experienced commercial drivers scan the road ahead by roughly how much travel time?
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Answer B: About 12 to 15 seconds
Looking 12 to 15 seconds ahead gives a heavy vehicle enough room to slow or change lanes smoothly instead of reacting late.
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26. An automatic transmission is left in its normal drive position as the vehicle rolls down a long grade. What does it tend to do?
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Answer A: Shift up as road speed rises, so engine braking falls away
An automatic left in drive keeps upshifting as speed builds, which is the opposite of what you want on a grade; that is why the driver must select a low range.
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27. During the walkaround you notice a bulge in the sidewall of a trailer tire. What does it indicate?
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Answer B: Damage inside the tire, which can lead to a sudden failure
A bulge means the internal structure has broken and only the rubber is holding the air, so the tire can burst without warning.
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28. When is tire pressure most accurately compared with the recommended figure?
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Answer B: When the tires are cold, before the vehicle has been driven
Recommended pressures are cold pressures, so a reading taken before the tires have heated up is the only one that can be compared directly.
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29. 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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30. How does California change the first-offense commercial disqualification when the driver was transporting placarded hazardous material?
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Answer A: The disqualification runs for three years instead of one
Section 15300 lengthens the one-year disqualification when the offense happened while the driver was transporting hazardous material required to be placarded.
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31. How long is a California commercial learner's permit valid?
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Answer D: 180 days, renewable for up to another 180 days without exceeding one year from the initial application
California issues the commercial learner's permit for a maximum of 180 days and allows one renewal of up to 180 more days, provided the expiration stays within one year of the initial application date.
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32. A tire may be regrooved only when what is true?
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Answer B: It carries a marking from the manufacturer showing that it is regroovable
Only casings built with extra rubber under the tread and marked regroovable by the manufacturer may be cut, because others would be grooved into the belts.
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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. Which of these is a major cause of skids in heavy vehicles?
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Answer C: Over-braking, over-steering, over-acceleration or driving too fast for conditions
Skids happen when the tires are asked for more grip than the road can give, which happens through braking, steering or accelerating too hard or simply too much speed.
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35. Why should you never shift gears while crossing railroad tracks?
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Answer A: You could miss the gear or stall and be stuck on the tracks
A stalled or coasting vehicle on the tracks has no way to clear quickly, so choose the gear before the crossing and do not shift until you are across.
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36. What is required of the hooks, rails, rings and anchor points that tiedowns attach to?
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Answer A: They must be part of the vehicle and strong enough for the load being secured
A tiedown is only as strong as what it is hooked to, so anchor points must be proper vehicle fittings rated for the job.
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37. You find one lug nut missing from a wheel that has ten studs. What should you do?
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Answer C: Treat it as a defect and have it repaired before the vehicle is driven
Every missing fastener loads the others more heavily, and wheel separations usually begin with one nut that nobody replaced.
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38. You must steer hard around an obstacle at highway speed. What is the correct technique?
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Answer B: Avoid braking while turning, turn only as far as needed, and countersteer as soon as the obstacle is passed
Braking during a hard steering input can lock the wheels and start a skid, and turning back at once keeps the vehicle from running off the far side of the road.
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39. What are you checking on the mud flaps during the walkaround?
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Answer C: That they are securely attached, not torn and not dragging on the ground
A flap that is torn or hanging loose stops shielding following traffic from spray and stones, and a dragging flap can catch and tear away on the road.
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40. You need to pull off onto the shoulder because of a problem with the load. How should you communicate that to other drivers?
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Answer D: Signal the move, then switch on the four-way flashers once stopped
Other drivers need a signal before you leave the lane and a clear warning once the vehicle is stopped near the traffic lanes.
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41. A doctor prescribes you a medicine that can cause drowsiness. What should you do?
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Answer A: Tell the doctor what you drive and not drive while affected
Both prescription and over the counter medicines can make a driver unsafe, so the medical professional must know the job and the driver must stay out of the seat while affected.
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42. You are hauling an open box of loose gravel. What does that load require?
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Answer A: A cover, so that material cannot blow off or spill onto the road
Loose material that can be blown or spilled has to be covered so it does not come out of the body and strike traffic behind.
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43. 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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44. Which set of emergency equipment must be carried on a commercial motor vehicle?
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Answer D: A fire extinguisher, spare electrical fuses unless the vehicle has circuit breakers, and warning devices
The required kit is a properly charged and rated fire extinguisher, spare fuses when the vehicle uses them, and warning devices for a stopped vehicle.
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45. Where should a driver expect fog to form first?
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Answer D: In low ground, near water and in valleys
Cool moist air settles in low places, so fog patches appear in hollows, river valleys and near lakes before they appear anywhere else.
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46. What must the driver confirm about the required emergency equipment before a trip?
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Answer A: That it is in place, in working order and ready to be used
Federal rules require the driver to be satisfied that the emergency equipment is present and ready, because it is needed at the worst possible moment.
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47. Apart from the legal duty, what is the main practical reason for a thorough pre-trip inspection?
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Answer A: It finds problems that could cause a breakdown or a crash before the vehicle is on the road
A defect found in the yard is an inconvenience, while the same defect found at highway speed can be a crash, so the inspection is where problems are cheapest to fix.
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48. On a tractor with a sliding fifth wheel, what does moving the fifth wheel forward do?
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Answer A: Puts more of the trailer weight onto the steering axle
Moving the coupling point forward transfers weight from the drive axles to the steering axle, which is how a driver corrects a drive axle that is over the limit.
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49. Which of these is NOT on the federal list of parts and accessories the driver must be satisfied are in good working order before driving?
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Answer D: The seat cushion upholstery
The federal pre-trip rule names brakes, steering, lights and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels and rims, and emergency equipment; seat upholstery is not on that list.
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50. Where are the OVERSIZE LOAD signs normally carried on a vehicle moving under such a permit?
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Answer A: On the front and the rear of the vehicle
The warning signs face the traffic that meets the load and the traffic that comes up behind it, so they go on the front and the rear.