Pennsylvania PennDOT CDL General Knowledge Practice Test 2
Test 2 of 5. Pick an answer for each question to see if it is right and why; your score appears at the end. You need 56 correct answers to pass, the same ratio as the real Pennsylvania test.
- Questions70
- Correct to pass56
- Passing score80%
- Minimum age18 years
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1. 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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2. Which vehicle is most likely to be pushed around by a strong crosswind?
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Answer B: An empty van trailer
A large flat side with very little weight behind it gives the wind the most surface and the least resistance, which is the empty van trailer.
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3. 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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4. You need fuel and the canopy over the pumps is low. What is the safe way to handle the clearance?
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Answer B: Stop and check the height at the entrance and at the way out before committing
Clearance can differ at the entry, under the canopy and at the exit, and a sloping approach changes the effective height, so both ends have to be checked.
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5. 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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6. A commercial vehicle stops on the shoulder of an undivided two-lane road that carries traffic in both directions. Where do the warning devices go?
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Answer B: Within 10 feet of the vehicle, plus 100 feet to the front and 100 feet to the rear
On a two-way road the devices must mark the vehicle itself and warn traffic approaching from each direction, and they must be in place within ten minutes.
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7. Cargo falls from your trailer and causes a crash behind you. Who is likely to answer for it?
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Answer C: The driver and the carrier, since securing the load on the road is their duty
Whoever loaded the vehicle, the driver and the carrier are responsible for the load being secure while it is on the road.
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8. An overpass you have driven under before now has a fresh layer of pavement on the road below it. Why does that matter?
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Answer B: The new layer raises the road and reduces the clearance
Repaving lifts the road surface, so the real clearance under a structure can be less than the height posted on it.
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9. What is checked in step six of the seven-step method?
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Answer D: The turn signals and the stop lights, checked from outside the vehicle
Step six returns to the cab to switch on the signal and stop lamps, then checks each one from outside, because those lamps are not lit during the earlier light check.
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10. Your drive wheels start to spin and the rear begins to slide while you accelerate on a slick surface. What should you do?
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Answer B: Stop accelerating and, if the vehicle has a manual transmission, push in the clutch
An acceleration skid ends when the drive wheels stop pushing, so easing off the throttle and disengaging the clutch lets them regain grip.
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11. What does mountain driving demand that flat country driving does not?
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Answer D: Lower gears and constant allowance for gravity
In the mountains gravity works for you on the climb and against you on the descent, so gear selection and speed control matter far more than on level road.
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12. How soon after passing the Pennsylvania commercial knowledge test can the skills test be taken?
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Answer C: After 15 days from passing the knowledge test and receiving the permit
Pennsylvania does not allow commercial skills testing until 15 days after the knowledge testing is passed and the permit is issued.
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13. What extinguisher rating is required on a vehicle carrying hazardous materials in amounts that need placards?
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Answer B: 10 B:C or more
Placarded loads carry a much higher fire risk, so the required extinguisher rating rises to at least 10 B:C.
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14. 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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15. 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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16. 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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17. 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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18. 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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19. How does a driver keep a vehicle with a manual transmission from rolling back when starting on an upgrade?
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Answer D: Partly engage the clutch before the right foot leaves the brake, or hold the vehicle with the parking brake until the engine pulls
Something has to hold the vehicle during the instant the foot moves from the brake to the accelerator, and that is either the clutch at its engagement point or the parking brake.
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20. A hazard suddenly appears ahead and you must act. Which is usually the faster way to avoid it in a heavy vehicle?
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Answer B: Steering around it, because you can usually turn faster than you can stop
Stopping distance at speed is very long, so a quick turn out of the way, when there is room, avoids the crash sooner than braking.
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21. What information does an inspection decal on a commercial vehicle carry?
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Answer B: The date of the inspection, where the inspection report is kept, and information identifying the vehicle
The decal shows when the inspection was done, the name and address of the entity that holds the inspection report, and which vehicle it belongs to, so an officer can confirm the inspection at a glance.
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22. A strap runs from an anchor point on one side of the trailer, over the load, and down to an anchor point on the opposite side. How much of its working load limit counts toward the total required?
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Answer C: All of it
A tiedown that is anchored on one side, passes over or around the cargo and is anchored on the other side counts its full working load limit toward the aggregate figure.
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23. A driver is tailgating you, honking and making gestures. What is the best response?
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Answer A: Do not make eye contact, ignore the gestures and give the driver room to get past
Engaging an aggressive driver only escalates the situation; the safest move is to stay calm, avoid eye contact and let the driver get by.
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24. Why is a sudden, sharp lane change dangerous in a loaded heavy vehicle?
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Answer D: The vehicle can lean far enough to roll over, especially when the load sits high
A quick swerve throws the weight of a tall, heavy load sideways, and a rollover can begin before the tires ever slide.
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25. Some commodities have their own detailed securement rules on top of the general ones. Which list is made up of such commodities?
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Answer C: Logs, metal coils, paper rolls, concrete pipe and crushed vehicles
The cargo securement rules add specific requirements for particular commodities, including logs, dressed lumber, metal coils, paper rolls, concrete pipe, intermodal containers, vehicles, crushed cars, roll on containers and large boulders.
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26. What tells a driver when to shift up in a vehicle with a manual transmission?
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Answer C: Engine speed in rpm together with road speed
Shift points are judged from engine rpm and road speed, using the operating range the manufacturer specifies for that engine.
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27. While you are driving, what should you do to catch a developing problem with the vehicle?
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Answer A: Check the gauges regularly and pay attention to unusual sounds, smells or vibrations
Inspection continues during the trip: gauges, mirrors and your senses can reveal a problem long before a warning light does.
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28. 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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29. 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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30. You are given a ratchet strap with a deep cut along one edge. What should you do?
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Answer C: Do not use it; a damaged tiedown cannot be relied on to hold its rated load
Cuts, burns, knots and broken stitching weaken a strap far below its marked working load limit, so it must be taken out of service.
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31. Your vehicle begins to hydroplane on a wet road. What should you do?
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Answer B: Release the accelerator and push in the clutch so the wheels can turn freely and regain grip
Hydroplaning tires are riding on water; slowing without braking lets them settle back onto the road and grip again.
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32. 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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33. Why should a retarder be switched off when the road is wet, icy or snowy?
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Answer C: It can make the drive wheels skid when traction is poor
A retarder slows the drive wheels only, and on a slippery surface that braking force can break their traction and start a skid.
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34. 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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35. 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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36. You are stopped in traffic on a steep upgrade behind another truck. How much space should you leave in front?
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Answer A: Enough that you can pull away without rolling back into the vehicle behind you
Room ahead lets you get moving smoothly on a grade instead of having to hold the vehicle perfectly still or roll back toward the traffic behind.
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37. Why must the downshift be finished before you reach a steep downgrade or a sharp curve rather than during it?
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Answer D: Because once your speed is too high you may not get into any gear at all
If you wait until speed has built up, the lower gear may refuse to engage and you can be left in neutral with no engine braking at all.
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38. You are driving past a park where children are playing close to the curb. What is the correct assumption?
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Answer A: A child may run into the street without looking
Children act on impulse and do not judge traffic well, so a driver has to expect one to enter the road and slow down in advance.
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39. The car in the next lane still has snow covering most of its windows. What should you assume?
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Answer C: That driver cannot see you and may move into your lane
A driver whose view is blocked cannot see the vehicles around, so you should assume you are invisible and stay out of that vehicle path.
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40. How much is the commercial driver license restoration fee following a suspension for operating an uninsured commercial vehicle in Pennsylvania?
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Answer A: 202 dollars
Pennsylvania sets the commercial driver license restoration fee at 202 dollars, higher than the 94 dollar fee for a standard license restoration.
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41. You are backing into a yard where electrical wires cross overhead. What is the main concern?
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Answer C: The wires may hang lower than the top of your vehicle
Overhead space has to be checked like any other space around the vehicle, because wires and cables are often lower than they look from the cab.
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42. 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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43. When should the horn of a commercial vehicle be used?
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Answer C: Only when it is needed to avoid a crash
An air horn is loud enough to startle other road users, so it is a warning device rather than a way to comment on other drivers.
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44. Before starting a trip, what must the driver confirm about the weight of the loaded vehicle?
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Answer A: That it is within the legal gross and axle limits for the route being driven
Overweight vehicles brake poorly, damage tires and suspension components, and can be put out of service at a scale, so weight is checked before the wheels turn.
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45. Why does extra weight make a long downgrade more dangerous even when the brakes are in good order?
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Answer B: Gravity adds to the momentum and the brakes heat up faster
The heavier the vehicle, the more energy the brakes must turn into heat, and heat is exactly what makes brakes fade on a long descent.
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46. 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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47. You are hauling a sealed trailer and have been told in writing not to open it. How does that affect the en route cargo checks?
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Answer C: You do not have to inspect the cargo itself, but the vehicle and weight are still yours
The en route cargo inspection rule does not apply to a driver of a sealed vehicle who has been ordered not to open it, but every other responsibility, including legal weight, remains.
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48. 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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49. When speed doubles, what happens to braking distance?
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Answer D: It becomes roughly four times as long
Braking distance rises with the square of speed, so twice the speed needs about four times the distance to stop.
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50. Your speedometer stops working during the pre-trip check. How should it be treated?
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Answer D: As a defect, because the driver cannot judge and control speed without it
A working speedometer is required equipment, because judging speed by feel in a heavy vehicle is unreliable and speed governs stopping distance.
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51. You have countersteered to correct a rear-wheel skid and the vehicle straightens out. What must you be ready for next?
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Answer D: The vehicle may swing back the other way, so you must steer again to correct it
A vehicle coming out of a skid tends to overshoot and swing in the opposite direction, and the driver must be ready to countersteer a second time.
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52. 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.
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53. Your windshield washer reservoir is empty and rain and road spray are expected. What should you do?
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Answer D: Fill it before the trip, because you need the washers to keep the windshield clear
Wipers alone smear the film of oil and grit thrown up by traffic, so the washers are part of keeping a usable view of the road.
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54. 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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55. Why does a heavy vehicle need a much larger gap than a car in order to cross or enter traffic?
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Answer C: Because it accelerates slowly and needs far more road and time to clear the intersection
Slow acceleration combined with the length of the vehicle means a gap that would feel comfortable in a car is nowhere near enough.
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56. Loading heavy freight on top of lighter freight has what effect on the vehicle?
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Answer B: It raises the center of gravity and makes a rollover more likely
A high center of gravity lets the vehicle tip more easily in curves or during a sudden swerve.
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57. In the seven-step method, what comes immediately after starting the engine and inspecting inside the cab?
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Answer D: Turn off the engine and check the lights
Step four shuts the engine down and switches on the lamps needed for driving so the driver can leave the cab and confirm they actually work.
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58. How should a driver use brakes fitted with an antilock system during an emergency stop?
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Answer C: Brake as usual and keep enough pressure to stay in control while steering around the hazard
The system only works when the brakes are applied hard enough for it to act, so the driver keeps pressure on and steers while the system prevents lockup.
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59. 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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60. 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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61. During a stop you find a package in the trailer leaking an unknown chemical. What should you do?
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Answer C: Keep clear, keep others away and get help without touching the package
A driver without the training and equipment does not handle a leak; the job is to protect people from the material and get qualified help to the scene.
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62. What is normally required in order to move an over-width or over-length load?
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Answer B: A special permit along with warning devices such as flags and signs
Oversize movements need a permit plus marking devices, and travel is often limited to certain hours or routes.
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63. 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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64. What is wrong with resting your foot on the clutch pedal between shifts?
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Answer B: It slowly wears the clutch out, because the pressure plate is never fully engaged
Any weight on the pedal partly disengages the clutch, so it slips and wears; the foot belongs off the pedal once the shift is finished.
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65. Which components on a typical engine are driven by belts that must be checked for wear and tension?
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Answer D: The alternator, the water pump and, on many vehicles, the air compressor
Belts drive accessories such as the alternator, the water pump and the air compressor, so one failed belt can take out charging, cooling or air supply.
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66. A car ahead of you keeps drifting within its lane and moving unevenly. What should you assume?
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Answer C: The driver may be distracted, lost or impaired
Unsteady lane keeping is a classic clue to a driver who is not in full control, so the safe response is to keep back and give plenty of room.
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67. Why is a leak in the exhaust system especially dangerous in cold weather?
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Answer A: Carbon monoxide can build up inside a closed cab
In winter the windows are shut and the heater is running, so exhaust gas that escapes early can reach the driver and cause drowsiness or worse.
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68. You are hauling a load of steel plate that is well within every weight limit but is stacked five feet high on a flatbed. What is the main concern?
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Answer A: The center of gravity is high, so the rig will roll more easily in a curve
Legal weight does not make a load safe; height raises the center of gravity and it is height, not weight alone, that decides how readily the vehicle rolls over.
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69. On a wet road, a commercial driver should reduce speed by roughly how much?
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Answer C: By about one third
Cutting speed by roughly a third, for example from 55 to about 35 mph, restores a margin for the traction lost on a wet surface.
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70. 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.