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Illinois CDL General Knowledge study materials
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Illinois CDL General Knowledge practice questions

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Question 1Vehicle Inspection

Before starting a trip in a commercial vehicle, the driver should perform a pre-trip inspection primarily to:

  1. Find defects that could cause a breakdown or crash before the vehicle goes on the road Correct answer.
  2. Confirm the vehicle's registration paperwork is filed in the cab
  3. Verify that the cargo has been fully loaded by the shipper
  4. Measure the exact fuel economy the vehicle will achieve on the route

Explanation

The purpose of the pre-trip inspection is safety: you look for defects in tires, brakes, lights, steering, and coupling that could lead to a breakdown or crash. Paperwork and fuel economy may matter, but they are not the reason the inspection is required.

Question 2Vehicle Inspection

During a pre-trip inspection you find a brake drum with a visible crack. What is the correct action?

  1. Note it on the inspection report and drive until the next scheduled service
  2. Cover the crack with tape and recheck it at the next stop
  3. Reduce speed by 10 mph and continue the trip
  4. Place the vehicle out of service until the defect is repaired Correct answer.

Explanation

A cracked brake drum is a serious defect that can lead to brake failure, so the vehicle must not be driven until it is repaired. Defects that affect safe operation put the vehicle out of service, and the driver must report them.

Question 3Vehicle Inspection

When checking the engine compartment during a pre-trip inspection, which item should you verify?

  1. That the battery cables are disconnected
  2. That the alternator belt is tight and not frayed Correct answer.
  3. That the coolant is above the hot full mark with the engine running
  4. That the oil dipstick reads below the add line

Explanation

Belts should be checked for tightness, cracks, frays, and glazing because a failed belt stops the alternator and water pump. Coolant is checked cold at the proper level, oil should be between add and full, and battery cables must be connected and secure.

Question 4Vehicle Inspection

How should you check the slack adjusters on a vehicle with air brakes during the pre-trip inspection?

  1. With air pressure at zero, measure the distance from the drum to the frame
  2. With the engine off, push each slack adjuster by hand to see if it wiggles
  3. With the parking brake released and the brakes applied, check that the pushrod does not move more than about one inch Correct answer.
  4. With the wheels removed, inspect the adjuster splines directly

Explanation

With the brakes released and then applied, a properly adjusted slack adjuster should allow no more than about one inch of pushrod travel. Excessive travel signals the brakes are out of adjustment and need service before driving.

Question 5Vehicle Inspection

You are inspecting a tractor-trailer and notice the fifth wheel jaws are not completely closed around the kingpin. What should you do?

  1. Chock the trailer wheels and tow the trailer to a shop
  2. Lock the jaws by hand and proceed if they stay shut
  3. Drive slowly and recheck the coupling after a few miles
  4. Do not move the vehicle until the coupling is corrected and secure Correct answer.

Explanation

An improperly closed fifth wheel can release the trailer while moving, so the vehicle must stay parked until the coupling is fixed. The driver should verify the jaws are locked and the release handle is secured before moving.

Question 6Vehicle Inspection

When performing a pre-trip inspection on a bus, which item must be checked that is not part of a typical tractor-trailer inspection?

  1. The trailer landing gear is fully raised
  2. The emergency exit doors and windows operate properly Correct answer.
  3. The glad hands are sealed with coupler gaskets
  4. The kingpin is greased and free of cracks

Explanation

Passenger vehicles carry riders, so emergency exits, windows, and doors must be checked to confirm they open and function. Landing gear, glad hands, and kingpins belong to tractor-trailer coupling systems, not to a bus.

Question 7Vehicle Inspection

During the walk-around inspection, how should you check that the parking brake holds?

  1. Press the brake pedal hard while the engine is off and listen for air leaks
  2. Apply the trailer hand valve and watch the air gauge drop
  3. Set the parking brake, put the vehicle in a low gear, and gently try to pull forward to see if it holds Correct answer.
  4. Release the parking brake and roll forward to see if the vehicle stops

Explanation

To test the parking brake, set it, place the transmission in a low gear, and gently attempt to move; the vehicle should not move. This confirms the brake can hold the vehicle when parked.

Question 8Vehicle Inspection

When checking tires during a pre-trip inspection, you should look for:

  1. Proper inflation, tread depth, and damage such as cuts or bulges Correct answer.
  2. The valve stem caps being the same color
  3. The brand name matching on all axles
  4. Only that the tires are black and round

Explanation

Tires must be checked for correct inflation, adequate tread depth, and defects like cuts, bulges, or exposed cords. These conditions affect traction and can cause blowouts.

Question 9Vehicle Inspection

After completing the pre-trip inspection, what should the driver do with the inspection report?

  1. Keep it and submit it as required by the carrier's procedures Correct answer.
  2. Discard it after the trip ends
  3. Hand it to the shipper at the destination
  4. Mail it to the state licensing agency

Explanation

The driver must complete and sign the inspection report and submit it according to the carrier's procedures so defects are documented and repaired. The report is part of the required recordkeeping.

Question 10Vehicle Inspection

During the pre-trip inspection, you check the lights and find the left turn signal does not flash. What does this indicate?

  1. A defect that can wait until the next quarterly inspection
  2. A defect that must be corrected before the vehicle is operated Correct answer.
  3. A normal condition because turn signals are optional
  4. A problem only if driving at night

Explanation

Turn signals are required safety equipment, and a non-functioning signal is a defect that must be repaired before driving. Operating with inoperative required lights is a violation and a hazard.

Question 11Vehicle Inspection

When inspecting the coupling system on a tractor-trailer, you should check the safety latch on the fifth wheel to ensure it:

  1. Is tied back with wire for easier uncoupling
  2. Rests loosely against the frame
  3. Is secured over the release handle so the coupling cannot open Correct answer.
  4. Is removed to allow the handle to move freely

Explanation

The safety latch must be closed over the release handle to prevent the fifth wheel from accidentally opening while the vehicle is moving. A missing or open latch is a serious coupling defect.

Question 12Vehicle Inspection

You are checking the engine compartment and see the power steering fluid is below the minimum mark. What is the proper response?

  1. Ignore it because power steering fluid does not affect safety
  2. Add the specified fluid and check for leaks before operating Correct answer.
  3. Drive the vehicle and check the level after the trip
  4. Fill the reservoir with water to reach the mark

Explanation

Low power steering fluid can cause loss of steering assist, so the correct fluid should be added and any leak investigated before driving. Steering is a critical safety system.

Question 13Vehicle Inspection

During a pre-trip inspection of an air brake system, the air pressure should build to the governor cut-out level and then:

  1. Drop immediately to zero
  2. Continue rising until the safety valve releases
  3. Hold steady without excessive leaks Correct answer.
  4. Fluctuate rapidly as the compressor cycles

Explanation

After the compressor reaches governor cut-out, pressure should hold steady; a rapid drop indicates a leak that must be fixed. The system should build pressure normally and maintain it.

Question 14Vehicle Inspection

While inspecting a trailer, you notice the landing gear is only partly raised and hangs low. Why is this a concern?

  1. It improves fuel economy by reducing drag
  2. It is required to be down for proper weight distribution
  3. It keeps the trailer brakes applied while driving
  4. It can strike the road or obstacles and damage the gear or cause a crash Correct answer.

Explanation

Landing gear must be fully raised and secured; if it hangs low it can hit the pavement, railroad crossings, or debris and cause damage or loss of control. It is not part of the braking or weight distribution system while driving.

Question 15Vehicle Inspection

You are checking the exhaust system during a pre-trip inspection. Which condition requires attention?

  1. A small amount of condensation at the tailpipe
  2. A properly secured muffler hanger
  3. Loose or leaking exhaust components near the cab Correct answer.
  4. A slight metallic color on the manifold

Explanation

Leaks or loose exhaust parts can allow carbon monoxide to enter the cab, which is dangerous to the driver. Exhaust components must be secure and free of leaks.

Question 16Vehicle Inspection

A driver finds that the steering wheel has excessive free play during the pre-trip inspection. How should this be handled?

  1. Record it and continue the trip if the roads are straight
  2. Inflate the front tires to the maximum pressure and proceed
  3. Compensate by steering more slowly while driving
  4. Report it and do not operate the vehicle until it is repaired Correct answer.

Explanation

Excessive steering free play means the steering system is worn or loose and can cause loss of control, so the vehicle must be repaired before operation. The defect must be reported.

Question 17Vehicle Inspection

During a pre-trip inspection, you must verify that the brake lights and the antilock braking system (ABS) warning light behave correctly. What is the expected ABS light behavior?

  1. It should stay on continuously whenever the engine runs
  2. It should never illuminate at any time
  3. It should flash only when the parking brake is set
  4. It should come on briefly when the ignition is turned on and then go out Correct answer.

Explanation

The ABS warning light should illuminate briefly as a bulb check when the ignition is turned on and then go out if the system is functioning. A light that stays on indicates an ABS fault that needs attention.

Question 18Vehicle Inspection

You are inspecting a loaded flatbed trailer and notice the cargo straps have slack in them. What is the correct action before departure?

  1. Add weight to the front of the trailer to tighten the straps
  2. Remove the straps so they do not flap in the wind
  3. Leave the straps as they are because cargo settles in transit
  4. Retighten the straps and verify the cargo is secured to the required standard Correct answer.

Explanation

Cargo must be secured against shifting, and slack straps allow movement that can cause loss of control or spilled loads. The driver should retighten and verify securement before moving.

Question 19Vehicle Inspection

During the pre-trip inspection, a driver checks the coolant level and finds the reservoir empty. Which statement best explains why this matters?

  1. It means the oil level is also low
  2. It is normal and requires no action
  3. An empty reservoir may indicate a leak that could lead to overheating and engine damage Correct answer.
  4. It only matters in freezing weather

Explanation

An empty coolant reservoir can signal a leak or low coolant, which may cause overheating and serious engine damage during the trip. The cause should be found and the level corrected before departure.

Question 20Vehicle Inspection

You are about to leave the terminal and realize you have not checked the fire extinguisher and emergency equipment. What is the correct approach?

  1. Carry a spare extinguisher instead of checking the mounted one
  2. Ask a passenger to check it while you drive
  3. Complete the check of required emergency equipment before departure Correct answer.
  4. Skip it because emergency equipment is only checked annually

Explanation

Required emergency equipment, including a charged fire extinguisher and warning devices, must be checked as part of the pre-trip inspection before the vehicle departs. Missing or discharged equipment leaves the driver unprepared for an emergency.

Question 21Basic Control of Your Vehicle

You are driving a tractor-trailer at highway speed and need to slow for a construction zone ahead. What is the safest way to reduce speed?

  1. Shift to neutral and use the brakes only in the final few hundred feet
  2. Push the clutch in and coast while applying light steady brake pressure
  3. Release the accelerator and let the engine and trailer drag slow the rig gradually Correct answer.
  4. Press the brake pedal firmly once and hold it until you reach the posted limit

Explanation

Large combination vehicles need gentle, progressive braking, so lifting off the throttle and letting engine drag and rolling resistance bleed off speed keeps the rig stable and gives following traffic time to react. Hard single brake applications and coasting in neutral both reduce your control, and on slick pavement a locked wheel can lead to a jackknife.

Question 22Basic Control of Your Vehicle

Why should you avoid riding the brake pedal on a long downgrade in a heavy truck?

  1. Brake fade from overheating can leave you without stopping power Correct answer.
  2. It causes the engine to over-rev and damage the valves
  3. It will overcharge the air compressor and trip the governor
  4. The brake lights will confuse drivers behind you

Explanation

Continuous light braking builds heat faster than the drums and shoes can shed it, and once the lining gets hot enough, friction drops off and the brakes fade. The correct technique is to select a low gear before the grade, use engine braking as the primary retarder, and apply brakes in short, firm applications when needed.

Question 23Basic Control of Your Vehicle

When must you use your four-way flashers while driving?

  1. Whenever you are following another commercial vehicle
  2. Only when you are stopped on the shoulder at night
  3. Whenever you are traveling below the posted minimum speed limit
  4. When you are moving slowly enough to be a hazard to other traffic Correct answer.

Explanation

Hazard lights warn other drivers that your vehicle is moving unusually slowly and may be a hazard, such as when climbing a steep grade under a heavy load. They are not meant for ordinary driving, for following another truck, or as a substitute for proper parking lights and triangles when stopped.

Question 24Basic Control of Your Vehicle

What is the correct procedure for starting a manual-transmission heavy truck from a stop on a level road?

  1. Use first gear, release the clutch smoothly, and apply power gradually Correct answer.
  2. Start in a high gear and slip the clutch to avoid wheelspin
  3. Rev the engine high and dump the clutch to prevent stalling
  4. Start in neutral and shift into first once the truck is rolling

Explanation

A loaded tractor-trailer needs the lowest practical gear and a smooth, progressive clutch release so the drivetrain takes up the load without shock. Dumping the clutch or starting in a tall gear can stall the engine, damage the clutch, or cause the trailer to lurch.

Question 25Basic Control of Your Vehicle

You are backing a tractor-trailer into a loading dock on the driver's side. Which practice is correct?

  1. Back quickly so you spend less time in the blind area
  2. Back with the trailer angled sharply to shorten the maneuver
  3. Rely on the backup alarm to warn people behind the trailer
  4. Use the mirrors, get out and check, and use a helper when possible Correct answer.

Explanation

Backing a large combination vehicle is the highest-risk maneuver you perform, so you check the area yourself, use both mirrors, and have a spotter guide you whenever one is available. If you lose sight of the spotter, you stop immediately.

Question 26Basic Control of Your Vehicle

What does the pivot point in a tractor-trailer refer to when you are turning?

  1. The point where the fifth wheel contacts the kingpin
  2. The rear wheels of the tractor, around which the trailer pivots Correct answer.
  3. The center of the trailer's rear axle group
  4. The point where the front axle steers the cab

Explanation

In a tractor-trailer the effective pivot point is the tractor's rear axle area, so the trailer cuts the corner and tracks inside the path the cab takes. That is why you must swing wide before a turn and watch the trailer's rear wheels in the mirrors through the maneuver.

Question 27Basic Control of Your Vehicle

How does the posted speed limit apply to a large commercial vehicle on a curve marked with an advisory speed?

  1. The advisory speed is a suggestion that can be ignored on dry pavement
  2. The advisory speed is the maximum safe speed for the curve in good conditions Correct answer.
  3. The advisory speed applies only to passenger cars
  4. You may exceed the advisory speed if the truck is empty

Explanation

Advisory speeds on yellow curve signs reflect the speed at which a vehicle can negotiate the curve safely in good conditions, and a loaded truck often needs to go slower because of its higher center of gravity and longer stopping distance. Entering a curve too fast risks a rollover or a drift into the opposing lane.

Question 28Basic Control of Your Vehicle

You are driving in dense fog on a rural interstate. Which combination of actions is most appropriate?

  1. Follow the taillights of the truck ahead closely for guidance
  2. Slow down, use low beams, and increase your following distance Correct answer.
  3. Maintain speed and use high beams to see farther ahead
  4. Turn on hazard flashers and continue at the posted limit

Explanation

Fog scatters light, so high beams actually reduce visibility by reflecting glare back at you; low beams aim under the fog. Reducing speed and opening following distance gives you the time and space to stop within the distance you can see.

Question 29Basic Control of Your Vehicle

What is the effect of a heavy load on your vehicle's stopping distance?

  1. It shortens stopping distance because the tires grip better
  2. It lengthens stopping distance and requires more following room Correct answer.
  3. It has no effect if the brakes are properly adjusted
  4. It only matters on wet pavement

Explanation

Added weight increases the kinetic energy the brakes must absorb, so a loaded truck takes noticeably longer to stop than an empty one and needs more following distance. The effect applies on dry pavement too, not only in rain.

Question 30Basic Control of Your Vehicle

When you must drive through standing water on the roadway, what should you do first?

  1. Apply the brakes hard while crossing
  2. Speed up to cross the water quickly
  3. Check the depth and the roadbed before entering Correct answer.
  4. Shift to a higher gear and coast through

Explanation

Standing water can hide a washed-out roadbed or be deep enough to stall the engine or float the vehicle, so you assess the depth and firmness of the surface before entering. If you do cross, you go slowly in a low gear and test your brakes gently afterward.

Question 31Basic Control of Your Vehicle

Why should you avoid making a sharp turn while braking hard in a tractor-trailer?

  1. The trailer brakes will release automatically
  2. The steering will lock and you will be unable to turn at all
  3. Combining hard braking and turning can cause a skid or jackknife Correct answer.
  4. The engine will stall from the load

Explanation

Tires have limited grip, and asking them to brake hard and turn sharply at the same time can exceed that limit, especially on a combination vehicle with a high center of gravity. The safe approach is to slow down before the turn, then steer through it with steady, smooth inputs.

Question 32Basic Control of Your Vehicle

You are descending a long mountain grade with a loaded trailer. Which gear should you select at the top of the grade?

  1. A gear low enough to hold a safe speed without heavy braking Correct answer.
  2. The highest gear so the engine runs cooler
  3. The same gear you used to climb the grade
  4. Neutral so you can use the brakes freely

Explanation

You choose the gear before the descent so engine braking can hold your speed without relying on the service brakes, which would overheat and fade. A useful rule is to descend in a gear no higher than the one you needed to climb the grade.

Question 33Basic Control of Your Vehicle

What is the correct way to use a retarder on a long downgrade in wet weather?

  1. Avoid retarders entirely because they damage the transmission
  2. Use it in a lower setting and be alert for drive-wheel skids Correct answer.
  3. Use the retarder only after the service brakes have faded
  4. Engage the retarder at full power as soon as the grade begins

Explanation

A retarder slows the drive wheels, and on a wet or slippery grade full retarder power can break traction and cause a skid, so you use a lower setting and watch for wheel slip. Retarders are a supplement to correct gear selection, not a substitute for it.

Question 34Basic Control of Your Vehicle

How should you adjust your following distance when driving a heavy truck at highway speeds?

  1. Match the gap that the vehicle ahead keeps from the one in front of it
  2. Allow at least one second for each ten feet of vehicle length, plus extra for speed Correct answer.
  3. Follow at the same distance as a passenger car, since brakes are larger
  4. Keep one truck length behind the vehicle ahead at all times

Explanation

The standard rule for large vehicles is at least one second of following distance for every ten feet of vehicle length at speeds under 40 mph, and more time as speed rises. For a 60-foot rig that is a minimum of six seconds at low speed, with additional space at highway speed and in poor conditions.

Question 35Basic Control of Your Vehicle

You feel the trailer begin to swing out to one side while you are braking on a slippery road. What should you do?

  1. Keep the brakes applied hard and steer against the swing
  2. Apply the trailer hand valve to stop the swing
  3. Accelerate to pull the trailer straight
  4. Release the brakes to let the wheels roll and steer to correct Correct answer.

Explanation

A trailer swing during braking usually means the wheels are losing traction, and releasing the brake lets them roll again so you can steer to straighten the rig. Holding the brakes or using the trailer hand valve while moving can worsen a jackknife.

Question 36Basic Control of Your Vehicle

Which statement about using your mirrors while driving a commercial vehicle is correct?

  1. Mirrors eliminate blind spots, so no head check is needed
  2. Convex mirrors give an accurate distance reading for passing vehicles
  3. Mirrors only need checking before you change lanes
  4. You should check mirrors regularly and know the blind spots they do not cover Correct answer.

Explanation

Mirrors must be checked often, but they never cover every area around a large vehicle, so you still need to know where your blind spots are and account for them. Convex mirrors show a wider field but make objects appear farther away than they are.

Question 37Shifting Gears

In a typical manual transmission, what is the purpose of the clutch?

  1. It multiplies engine torque before the power reaches the drive wheels
  2. It locks the rear wheels when the parking brake is applied
  3. It controls the speed of the engine at idle
  4. It temporarily disconnects engine power from the transmission so gears can be changed Correct answer.

Explanation

The clutch is the coupling between the engine and the transmission. Pressing the pedal releases that coupling so the engine and transmission can turn at different speeds while you select a gear. Releasing the pedal re-engages the connection smoothly.

Question 38Shifting Gears

You are driving a loaded tractor-trailer and need to downshift while climbing a long grade. When should you make the downshift?

  1. Before the engine loses power, while road speed is still high enough for the lower gear Correct answer.
  2. While holding the clutch pedal fully down through the rest of the climb
  3. After the engine has already begun to lug and lose speed
  4. Only after reaching the top of the grade

Explanation

A heavy vehicle loses speed quickly on a grade, so waiting until the engine lugs can leave you unable to complete the shift. Downshift while you still have enough road speed to match the lower gear. Coasting with the clutch depressed is unsafe and gives up engine braking.

Question 39Shifting Gears

What is the safest gear to be in when driving down a steep, long downgrade in a heavy vehicle?

  1. Neutral, so the brakes alone control speed
  2. A gear low enough that the engine and brakes hold the vehicle at a safe speed without riding the brakes Correct answer.
  3. Any gear, as long as the service brakes are applied firmly and continuously
  4. The highest gear available, to keep engine RPM low

Explanation

You should select a gear before the descent that lets engine braking hold a safe speed, using the brakes only to trim speed. This keeps the brakes cool and ready for an emergency. Coasting in neutral or riding the brakes can lead to brake fade and loss of control.

Question 40Shifting Gears

Why should you avoid coasting with the transmission in neutral or with the clutch pedal held down?

  1. It wears out the synchronizers faster than normal shifting
  2. It increases fuel consumption at highway speed
  3. It reduces your ability to accelerate and to use engine braking, and it is unsafe and often illegal Correct answer.
  4. It causes the differential to lock up

Explanation

Coasting removes the connection between engine and drive wheels, so you lose the ability to accelerate out of trouble and lose engine braking. Many jurisdictions prohibit coasting in neutral for this reason. Keeping the vehicle in gear preserves control.

Question 41Shifting Gears

When upshifting a non-synchronized (constant mesh) heavy truck transmission, what does double-clutching accomplish?

  1. It lets you skip the clutch entirely on the second shift
  2. It engages the parking brake automatically during the shift
  3. It increases engine RPM beyond the governed limit
  4. It matches the speed of the transmission gears so they engage without clashing Correct answer.

Explanation

A non-synchronized transmission needs the gear speeds matched before engagement. Double-clutching lets you release the clutch in neutral and adjust engine speed so the gears line up. This prevents grinding and allows a smooth shift.

Question 42Shifting Gears

You are driving a manual-transmission truck and the transmission will not go into the next gear; you hear grinding. What is the most likely cause?

  1. The tires are overinflated
  2. The engine oil level is too high
  3. The alternator belt is slipping
  4. The clutch is fully engaged and the gear speeds are not matched Correct answer.

Explanation

Grinding on a shift usually means the gear speeds are not matched and the clutch is not fully disengaged. Press the clutch fully and adjust engine speed to match the gear before trying again. Forcing the lever can damage the transmission.

Question 43Shifting Gears

What is the correct way to start a heavy manual-transmission truck moving from a stop on level ground?

  1. Engage first gear, release the clutch gradually to the friction point while applying light throttle, then release fully as the vehicle moves Correct answer.
  2. Release the clutch quickly while applying full throttle
  3. Hold the clutch at the friction point for the entire acceleration to keep it smooth
  4. Select a high gear to reduce wheelspin

Explanation

Smooth starts require a gradual release of the clutch to the friction point while adding light throttle. Once the vehicle is rolling, release the pedal fully so the clutch locks up and does not slip. This reduces wear and gives control.

Question 44Shifting Gears

A driver approaching a sharp turn in a heavy vehicle should do which of the following with regard to gear selection?

  1. Shift into a lower gear while in the middle of the turn
  2. Shift into neutral to coast through the turn
  3. Complete any downshift before entering the turn and stay in gear through it Correct answer.
  4. Upshift to the highest gear just before the turn

Explanation

Shifting during a turn can upset the vehicle and take your attention away from steering. Select the proper gear before the turn and keep it engaged so you have power and engine braking available. Coasting through a turn reduces control.

Question 45Shifting Gears

On a vehicle with a two-speed rear axle (splitter), what is the purpose of the splitter control?

  1. It changes the rear axle ratio between a high and low range to provide closer gear steps Correct answer.
  2. It engages the differential lock for traction
  3. It disengages the clutch automatically
  4. It controls the trailer brake proportioning valve

Explanation

A two-speed rear axle provides two ratios, often called high and low range, that split each transmission gear into finer steps. The splitter control selects the range so the driver can match engine speed to load and grade. It does not lock the differential or operate the clutch.

Question 46Shifting Gears

Which statement best describes progressive shifting in a heavy truck?

  1. Shifting only when the engine begins to lug
  2. Skipping gears to reach top gear as quickly as possible
  3. Running every gear to the governed maximum RPM before shifting
  4. Upshifting at low engine RPM and using each gear only up to the speed needed to reach the next gear Correct answer.

Explanation

Progressive shifting means shifting at relatively low RPM and using each gear only as long as needed to reach the next gear. This saves fuel and reduces engine wear. Running each gear to the governor or lugging the engine wastes fuel and strains components.

Question 47Seeing Hazards

While driving a tractor-trailer on an interstate, you notice a car in the adjacent lane drifting repeatedly toward the lane divider and then correcting. What is the safest way to respond to this hazard?

  1. Drop back or move away to increase your cushion, and prepare to react if the car crosses over Correct answer.
  2. Sound your air horn continuously until the car changes lanes
  3. Assume the driver is using a turn signal and maintain your speed and lane position
  4. Speed up to pass the car quickly before it drifts again

Explanation

A vehicle that drifts and corrects is a sign of an impaired, drowsy, or distracted driver, so you should treat it as an unpredictable hazard. Increasing your following distance or changing lanes gives you time and space to react if it swerves. Passing quickly puts your trailer alongside the car at the worst possible moment.

Question 48Seeing Hazards

What is the most reliable early warning that a driver ahead may be about to brake or turn?

  1. The vehicle's four-way flashers activating
  2. The vehicle's backup lights illuminating
  3. The vehicle's brake lights illuminating Correct answer.
  4. The vehicle's headlights switching from high to low beam

Explanation

Brake lights are the first visible signal that the driver ahead is slowing, and they appear before the vehicle actually loses much speed. Spotting them early lets you begin slowing and build space before the gap closes. Backup lights, headlight dimming, and hazard flashers do not reliably signal an impending stop in your lane.

Question 49Seeing Hazards

You are following a loaded flatbed on a two-lane road and see loose gravel and a tarp flapping at the rear of the load. How should this change your driving?

  1. Flash your headlights to warn the driver and stay directly behind
  2. Follow closer so other vehicles cannot cut in front of you
  3. Move to the left portion of your lane and maintain speed
  4. Increase your following distance and consider passing when it is safe Correct answer.

Explanation

A flapping tarp and loose gravel are signs that the load may shed debris, which can crack a windshield or cause a loss of control. Backing off keeps you out of the debris path and gives you time to react. Passing when legal and safe removes you from the hazard entirely.

Question 50Seeing Hazards

When entering a work zone with a flagger holding a SLOW paddle, what should you do with your speed and following distance?

  1. Maintain your posted-limit speed and keep your normal following distance
  2. Keep your speed but reduce your following distance
  3. Slow only after you pass the flagger's position
  4. Slow down as directed and increase your following distance Correct answer.

Explanation

Work zones compress lanes and put workers close to traffic, so the flagger's direction overrides the normal posted limit. You should also open up your following distance because sudden stops are common and rear-end crashes are frequent in work zones. Reducing space or delaying the slowdown removes your margin for error.