Louisiana OMV CDL General Knowledge Practice Test 4
Test 4 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 Louisiana test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. What does a front-end header board on a van or flatbed protect against?
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Answer A: Cargo moving forward toward the cab in a crash or hard stop
The header board, often called a headache rack, blocks forward movement of the load toward the driver.
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2. Under federal rules, which commercial vehicles must stop at every railroad crossing before proceeding?
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Answer D: Passenger buses and placarded hazardous materials vehicles
Buses carrying passengers and vehicles required to display hazardous materials placards must stop at crossings, while other commercial vehicles slow and check.
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3. What do the U-bolts on a leaf spring suspension do?
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Answer A: They clamp the spring assembly to the axle so it cannot move
U-bolts hold the spring pack tight against the axle, and a loose or broken U-bolt lets the axle slide out of place under load.
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4. What does safe practice require of a commercial driver who wants to eat, drink or read a delivery note?
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Answer B: Handle it before or after driving, not while moving
Anything that takes hands, eyes or attention away from the task belongs outside the driving time, not inside it.
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5. When traction is poor, such as on packed snow, how should you speed up?
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Answer C: Very gradually, so the drive wheels do not spin
Gentle throttle keeps the drive wheels from breaking traction, because spinning wheels give up both grip and directional control.
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6. Your right wheels drop off the pavement onto a soft shoulder. What is the correct recovery?
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Answer A: Stay on the shoulder, ease off the accelerator, brake gently only once speed is down to about 20 mph, then steer back sharply and countersteer at once
Bringing speed down on the shoulder first avoids a violent sideways jolt, and countersteering the instant the tires are back on the pavement keeps the vehicle out of the next lane.
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7. 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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8. In Louisiana, who may hold the H hazardous materials endorsement?
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Answer B: Only persons 21 years of age or above
Louisiana issues the H endorsement only to applicants who are at least 21 years old.
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9. How do you avoid the sharp lurch that comes at the very end of a stop in a heavy vehicle?
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Answer A: Ease off the brake pressure just before the vehicle actually comes to rest
A smooth stop is finished by reducing pedal pressure as the vehicle settles, so the suspension does not rock the cab and the load forward.
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10. A tire blows out at highway speed. What should the driver do first?
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Answer C: Hold the steering wheel firmly, stay off the brake and let the vehicle slow down
Braking while a tire is gone can pull the vehicle out of line, so the driver keeps it straight and lets speed fall before easing off the road.
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11. You are taking a tightly curved highway exit ramp in a long combination. Where should the tractor be placed within the lane?
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Answer D: Toward the outside of the curve, leaving room for the trailer to track inside
Because the trailer wheels cut to the inside of the curve, the tractor has to be kept out toward the outer edge so the trailer does not drop a wheel off the inside edge.
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12. 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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13. 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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14. 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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15. At 55 mph, about how far does a vehicle travel during a typical 3/4 second perception time plus 3/4 second reaction time, before the brakes even begin to work?
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Answer C: About 120 feet
Each 3/4 second at 55 mph covers about 60 feet, so perception and reaction together use up roughly 120 feet before braking starts.
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16. 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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17. What happens to braking distance when speed is doubled?
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Answer C: It becomes about four times longer
Braking distance grows with the square of speed, so doubling the speed multiplies both the braking distance and the force of an impact by about four.
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18. 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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19. A driver snores heavily, stops breathing briefly during the night and is tired all day despite long hours in bed. What should be suspected?
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Answer B: Sleep apnea
Sleep apnea repeatedly interrupts breathing during sleep, so the driver never gets true rest and stays dangerously drowsy during the day.
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20. During the walkaround you find the reflective conspicuity tape along the trailer caked with road grime. What should you do?
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Answer B: Clean it, because dirty reflective material cannot make the trailer visible at night
Reflective sheeting only works if light can reach it and bounce back, so a dirty strip leaves the trailer effectively unmarked to approaching traffic.
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21. Why must exhaust components be checked for contact with other parts of the vehicle?
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Answer B: Hot exhaust parts touching fuel lines, tires or wiring can start a fire
Exhaust pipes run hot enough to ignite fuel and melt insulation, so they must be kept clear of the fuel system, the tires and the electrical harness.
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22. You drive a 40 foot straight truck at 50 miles per hour in good conditions. What following distance does the rule of thumb call for?
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Answer A: 5 seconds
One second for every 10 feet of vehicle length gives 4 seconds, and one extra second is added for speeds above 40 miles per hour.
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23. 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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24. You have finished a lane change in a vehicle whose turn signal does not cancel by itself. What must you do?
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Answer D: Turn the signal off yourself
A signal left running tells other drivers you are about to move again, and they may act on that false information.
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25. 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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26. What must be checked about the cargo doors and any tarpaulin before a trip?
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Answer B: That the doors are closed and latched and that any tarp is tied down securely
An unlatched door or a loose tarp can swing open or tear free at speed, spilling cargo or blocking the view of the traffic behind you.
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27. A carrier operates commercial vehicles every day of the week. What weekly on-duty limit applies to its drivers?
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Answer A: 70 hours in 8 consecutive days
The limit is 60 hours in 7 consecutive days for a carrier that does not run every day, and 70 hours in 8 consecutive days for one that does.
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28. During a trip you stop for a break. Which items should you check before driving on?
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Answer B: Tires, wheels and rims, brakes, lights, reflectors, electrical connections and cargo securement
Critical items can change during a trip, so each stop is used to recheck the tires, wheels, brakes, lights, connections and cargo.
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29. You are told a posted bridge ahead has a weight limit lower than your gross weight. What must you do?
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Answer C: Take a route that avoids it, because a posted limit is a legal limit
A posted structure limit must be obeyed exactly as any other weight limit, so a heavier vehicle has to be routed around it.
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30. How long is the commercial learner's permit that Louisiana issues after an applicant passes the required knowledge tests?
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Answer C: 180 days
Louisiana issues a 180 day commercial learner's permit once the required tests are passed, and the skills test is then scheduled with a third party examiner.
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31. 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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32. You have just passed another vehicle on a two lane road. What tells you it is safe to return to your lane?
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Answer B: You can see the whole front of that vehicle in your right mirror
Seeing the entire front of the vehicle you passed in your mirror proves you are far enough ahead to move back over without cutting the driver off.
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33. During the engine compartment check, which leaks are you looking for?
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Answer D: Fuel, coolant, engine oil, power steering fluid and battery fluid
Every fluid in the compartment matters, because a fuel leak is a fire risk and a loss of coolant, oil, steering fluid or electrolyte can disable the vehicle.
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34. 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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35. You are moving an oversized load under a permit that requires a pilot vehicle. What is the pilot vehicle there to do?
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Answer B: Warn other traffic and check the route ahead for clearances and hazards
Escort or pilot vehicles warn approaching traffic and scout the route for low bridges, narrow spots and other hazards that a wide or long load cannot pass.
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36. Why does a driver use pull-ups while backing into a tight space?
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Answer C: To pull forward and start the approach again when the angle is going wrong
Stopping, pulling ahead and repositioning fixes a bad angle safely, and there is nothing wrong with needing more than one attempt.
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37. The paperwork shows a weight, but the load looks heavier than you expected. What should you do?
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Answer C: Weigh the vehicle, since you are the one answerable for driving it overweight
The driver is the one who can be cited for an overweight vehicle, so a doubtful weight is settled on a scale before the trip continues.
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38. A 60 foot combination traveling above 40 mph should hold how many seconds of following distance?
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Answer D: Seven seconds
Six seconds cover the 60 feet of vehicle length, and one extra second is added because the speed is above 40 mph.
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39. Why should you avoid using your lights to tell a following driver that it is safe to pass you?
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Answer B: You may misjudge the gap and the driver will act on your signal
The manual warns against signaling others to pass, because the responsibility for a head-on crash then rests on a judgment you could easily get wrong.
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40. What condition should the fifth wheel be in before you back under a trailer?
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Answer C: Jaws open, plate greased, and the fifth wheel tilted down toward the rear
The jaws have to be open to take the kingpin, the plate must be lubricated to prevent hard steering, and the fifth wheel is tilted down at the rear so the trailer apron can ride up onto it.
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41. How long must the record of a periodic inspection be kept?
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Answer A: Fourteen months
The periodic inspection report is retained for fourteen months from the date of the report, which covers the full twelve month cycle plus a margin.
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42. 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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43. What is the most common cause of a front-wheel skid, where the vehicle keeps going straight even though you turn the wheel?
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Answer B: Driving too fast for the conditions
A front-wheel skid usually comes from too much speed for the traction available; the only cure is to let the vehicle slow down and stop turning or braking so hard.
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44. 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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45. What does the commercial driver manual tell you to do with the parking brake when you leave your vehicle?
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Answer B: Apply the parking brake every time you leave the vehicle
The manual is explicit that the parking brake goes on whenever the driver leaves the vehicle, because once nobody is at the controls it is the only thing holding it.
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46. An unblocked article is 15 feet long. What is the minimum number of tiedowns?
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Answer B: Three
Two tiedowns cover the first 10 feet and one more is added for each further 10 feet or any part of it, so 15 feet needs three.
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47. What are you looking for on the brake drums during the walkaround?
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Answer B: Cracks, dents and any oil or grease that has reached the friction surface
A cracked or badly scored drum can break apart under braking heat, and oil or grease on the friction surface destroys the braking effort at that wheel.
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48. You press on a drive belt and it deflects far more than the others. What does that suggest?
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Answer C: The belt is too loose and the part it drives may not work properly
A belt with excessive play slips on its pulleys, so the accessory it drives turns too slowly or not at all under load.
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49. Under federal rules, what happens to a commercial driver found with any detectable amount of alcohol while operating a commercial vehicle?
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Answer D: The driver is placed out of service for 24 hours
Any measurable alcohol takes a commercial driver off the road for 24 hours, and a concentration of 0.04 percent or more brings a disqualification.
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50. How can a driver tell that a shipment includes hazardous materials?
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Answer B: The shipping paper describes them and the packages carry hazard warning labels
Hazardous materials are identified on the shipping paper with their shipping name and hazard class, and the packages themselves carry labels showing the hazard.