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OR CDL General Knowledge practice questions

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Question 1General CDL Knowledge (Oregon CDL Manual core)

Under the Oregon CDL rules, a driver must obtain a Commercial Driver License to operate which of the following vehicles on public roads?

  1. A passenger van designed to carry 12 people including the driver
  2. A combination vehicle with a gross combination weight rating of 26,001 pounds or more, provided the towed unit exceeds 10,000 pounds Correct answer.
  3. A single-unit rental truck with a gross vehicle weight rating of 24,000 pounds
  4. A pickup truck towing a small utility trailer with a combined weight under 10,000 pounds

Explanation

A CDL is required when the vehicle or combination meets the federal weight and configuration thresholds. For combinations, the gross combination weight rating must be 26,001 pounds or more and the towed unit must exceed 10,000 pounds. Vehicles below these thresholds generally do not require a CDL.

Question 2General CDL Knowledge (Oregon CDL Manual core)

Before backing a tractor-trailer, what is the safest first step?

  1. Turn the steering wheel fully to the right before moving
  2. Sound the horn twice and back immediately
  3. Rely on the convex mirrors only
  4. Get out and walk around the vehicle to check for obstacles and clearance Correct answer.

Explanation

Walking around the vehicle before backing lets you see obstacles, low clearance, and people that mirrors may hide. Mirrors have blind spots, especially directly behind and along the sides of a trailer. Checking the path on foot first is the standard safety practice taught in the manual.

Question 3General CDL Knowledge (Oregon CDL Manual core)

When driving a vehicle with air brakes, at what point should you test the brakes by stopping and checking for leaks?

  1. Only after the vehicle has been driven at highway speed for 30 minutes
  2. After the air pressure has built up to the governor cut-out level and the engine is shut off Correct answer.
  3. Only when the low air pressure warning buzzer sounds
  4. Immediately after starting the engine, before building air pressure

Explanation

The air brake check is performed with a fully charged system, so pressure must build to the governor cut-out before testing. With the engine off, you watch the gauge for pressure loss over a timed interval. Testing before pressure builds gives no meaningful reading.

Question 4General CDL Knowledge (Oregon CDL Manual core)

You are driving a loaded combination vehicle and need to stop on a downgrade. Which practice best controls your speed?

  1. Shift to neutral and use the service brakes continuously
  2. Pump the brakes rapidly and repeatedly the entire descent
  3. Apply the trailer hand valve to hold the vehicle while rolling
  4. Select a gear low enough that engine braking holds your speed and use the brakes sparingly Correct answer.

Explanation

Descending in a low gear lets engine compression control speed and keeps the service brakes cool for emergencies. Continuous or rapid braking overheats the drums and can lead to brake fade. Coasting in neutral removes engine braking and is illegal in most situations.

Question 5General CDL Knowledge (Oregon CDL Manual core)

When a front tire blows out on a loaded truck, what is the correct response?

  1. Accelerate to stabilize the vehicle
  2. Hold the steering wheel firmly, keep the vehicle straight, and slow gradually Correct answer.
  3. Release the steering wheel briefly to let the vehicle correct itself
  4. Brake hard immediately and steer for the shoulder

Explanation

A front blowout pulls hard toward the failed tire, so a firm grip and a straight path keep control. Hard braking or sudden steering can cause a loss of control or rollover. You should slow gradually and move off the road only after regaining stability.

Question 6General CDL Knowledge (Oregon CDL Manual core)

Oregon law requires a driver to stop before crossing a railroad grade when a train is within how many feet of the crossing?

  1. 2,000 feet
  2. 1,500 feet Correct answer.
  3. 500 feet
  4. 1,000 feet

Explanation

Oregon requires a stop when a train is approaching within 1,500 feet of the crossing, in addition to stop signals, gates, or a flagger. This distance gives a loaded commercial vehicle time to clear the tracks safely. Stopping is always required when warning devices are active.

Question 7General CDL Knowledge (Oregon CDL Manual core)

What is the purpose of the bridge formula in commercial vehicle weight enforcement?

  1. To limit the total number of axles a tractor-trailer may use
  2. To calculate the required stopping distance at highway speed
  3. To determine the minimum tire pressure for heavy loads
  4. To set maximum weight limits for axle groups based on the distance between them Correct answer.

Explanation

The bridge formula limits the weight carried on any group of axles based on the span between the first and last axle of that group. It protects bridges from concentrated loads that exceed their design capacity. It applies regardless of the number of axles as long as the span is measured correctly.

Question 8General CDL Knowledge (Oregon CDL Manual core)

Which of the following best describes the correct way to hold the steering wheel for maximum control?

  1. Both hands at the bottom of the wheel to avoid the airbag
  2. Both hands on opposite sides of the wheel, with thumbs hooked inside the rim
  3. One hand at the top of the wheel and one on the gear shift
  4. Both hands on the wheel, with thumbs resting along the outside of the rim Correct answer.

Explanation

Holding the wheel with both hands and thumbs outside the rim gives steady control and prevents thumb injury if the wheel kicks back. Hooking thumbs inside the rim is dangerous on rough roads or during a blowout. Both hands should remain on the wheel except when shifting.

Question 9General CDL Knowledge (Oregon CDL Manual core)

When must a driver use the four-way flashers on a commercial vehicle?

  1. Whenever driving below the posted speed limit
  2. When stopped on the shoulder or moving slowly enough to warn other drivers Correct answer.
  3. When passing another commercial vehicle
  4. Only when backing into a loading dock

Explanation

Four-way flashers warn other drivers that your vehicle is a hazard, such as when stopped on the shoulder or moving unusually slowly. They are not a substitute for turn signals or a way to justify speeding. Using them while driving normally can confuse other drivers.

Question 10General CDL Knowledge (Oregon CDL Manual core)

What does the term 'gross vehicle weight rating' (GVWR) represent?

  1. The combined weight of the tractor and trailer at the time of inspection
  2. The weight of the vehicle when empty
  3. The maximum safe loaded weight of the vehicle as specified by the manufacturer Correct answer.
  4. The weight of the cargo only

Explanation

GVWR is the manufacturer's maximum allowable total weight for the vehicle, including the vehicle, fuel, passengers, and cargo. It is a design limit, not a measured weight. Exceeding it can void the vehicle's safe operating envelope.

Question 11General CDL Knowledge (Oregon CDL Manual core)

A driver is approaching a curve posted with an advisory speed lower than the general limit. What should the driver do?

  1. Slow to the advisory speed before entering the curve Correct answer.
  2. Accelerate through the curve to maintain momentum
  3. Maintain the general speed limit because advisory signs are suggestions only
  4. Brake hard in the middle of the curve

Explanation

Advisory speeds reflect the safe speed for the curve under normal conditions, especially for heavy vehicles with a high center of gravity. Slowing before the curve keeps the vehicle stable and avoids braking mid-turn. Braking inside a curve can cause a skid or rollover.

Question 12General CDL Knowledge (Oregon CDL Manual core)

How far ahead should a commercial driver look while driving at highway speed?

  1. About 30 seconds ahead
  2. About 5 seconds ahead
  3. About 2 seconds ahead
  4. About 12 to 15 seconds ahead Correct answer.

Explanation

Looking 12 to 15 seconds ahead gives you time to spot hazards, plan lane changes, and react smoothly. At highway speed this translates to roughly a quarter mile. Looking too close limits reaction time.

Question 13General CDL Knowledge (Oregon CDL Manual core)

When is it legal to use a handheld mobile phone while operating a commercial motor vehicle in Oregon?

  1. When traffic is light and the call is brief
  2. When using the speakerphone function while holding the phone
  3. Never, because handheld use is prohibited for commercial drivers Correct answer.
  4. Only when parked at a rest area with the engine running

Explanation

Oregon and federal rules prohibit commercial drivers from holding a phone while operating a CMV. Hands-free use is allowed only in limited circumstances, and texting is always prohibited. The safest practice is to pull over and park before making a call.

Question 14General CDL Knowledge (Oregon CDL Manual core)

What is the correct procedure for coupling a tractor to a trailer?

  1. Connect the air lines before the trailer is secured to the tractor
  2. Check the fifth wheel is open, back under squarely, and tug-test after locking the jaws Correct answer.
  3. Lower the trailer onto the fifth wheel without checking the jaws
  4. Back under the trailer at an angle, then raise the landing gear

Explanation

The fifth wheel must be open and the tractor backed under squarely so the kingpin locks into the jaws. After locking, a tug test confirms the coupling before you raise the landing gear. Air lines are connected only after the trailer is secure.

Question 15General CDL Knowledge (Oregon CDL Manual core)

What is the proper way to check that the trailer is securely coupled to the tractor?

  1. Visually confirm the jaws are closed and pull forward gently against the trailer brakes Correct answer.
  2. Check the air pressure gauge only
  3. Ask a passenger to watch from the cab
  4. Rely on the sound of the coupling

Explanation

A visual check that the jaws are closed plus a gentle pull against the set trailer brakes confirms the kingpin is locked. This tug test is the standard verification before raising the landing gear. Relying on sound or gauges alone is unreliable.

Question 16General CDL Knowledge (Oregon CDL Manual core)

When driving a vehicle with a high center of gravity, what is the greatest risk during a sharp turn?

  1. Brake fade
  2. Rollover Correct answer.
  3. Loss of air pressure
  4. Tire blowout

Explanation

A high center of gravity makes a vehicle more likely to tip over when turning sharply or at excessive speed. Rollover risk increases with speed through the curve and with a full or top-heavy load. Slowing before the turn is the key preventive measure.

Question 17General CDL Knowledge (Oregon CDL Manual core)

What does the term 'space cushion' mean in defensive driving?

  1. The gap between the cab and the trailer during coupling
  2. The distance from the vehicle to the curb when parking
  3. The clear distance you keep around your vehicle to allow room to react Correct answer.
  4. The distance between the rear wheels of the tractor and trailer

Explanation

A space cushion is the buffer of clear distance kept around your vehicle so you have time to react to hazards. It includes following distance, side room, and space ahead for stopping. Maintaining it reduces the need for sudden maneuvers.

Question 18General CDL Knowledge (Oregon CDL Manual core)

Under Oregon rules, a commercial driver's blood alcohol concentration limit is which of the following?

  1. 0.10 percent
  2. 0.04 percent Correct answer.
  3. 0.02 percent
  4. 0.08 percent

Explanation

Commercial drivers are held to a stricter standard of 0.04 percent BAC while operating a CMV. This is lower than the 0.08 percent limit for non-commercial drivers. A conviction can disqualify the driver for a period of time.

Question 19General CDL Knowledge (Oregon CDL Manual core)

What is the correct action when your vehicle's air pressure warning buzzer and light activate while driving?

  1. Shift to a lower gear and use engine braking, then stop safely as soon as possible Correct answer.
  2. Continue driving until the next scheduled stop
  3. Pump the brakes repeatedly to build pressure
  4. Turn off the engine immediately in the travel lane

Explanation

A low air pressure warning means the system is losing pressure and braking power may soon be lost. The safe response is to slow using engine braking and get off the road before the spring brakes apply. Stopping in the travel lane creates a collision hazard.

Question 20General CDL Knowledge (Oregon CDL Manual core)

When must a driver perform a pre-trip inspection?

  1. Before every trip, regardless of distance Correct answer.
  2. Once per week if the vehicle is used daily
  3. Only when the vehicle was used by another driver
  4. Only before long trips over 100 miles

Explanation

A pre-trip inspection is required before each trip so defects are found before they cause a breakdown or crash. It covers brakes, lights, tires, coupling, and other safety items. Daily or weekly intervals do not satisfy the requirement.

Question 21General CDL Knowledge (Oregon CDL Manual core)

What is the correct way to check tire tread depth on a commercial vehicle?

  1. Press the tire with your thumb
  2. Use a tread depth gauge in the major grooves Correct answer.
  3. Estimate it visually from the driver's seat
  4. Check only the outside edge of the tire

Explanation

Tread depth must be measured with a gauge in the major grooves to confirm it meets the minimum. Visual estimates and thumb pressure are unreliable. Checking only the outer edge misses wear across the tread face.

Question 22General CDL Knowledge (Oregon CDL Manual core)

When should a driver use the engine brake (retarder) on a long downgrade?

  1. When approaching a stop sign at the bottom
  2. Only when the road is icy
  3. Only after the service brakes begin to fade
  4. At the top of the grade, before speed builds Correct answer.

Explanation

Engine brakes work best when engaged at the top of the grade before speed builds. Waiting until brakes fade removes your margin of safety. Retarders should be used with care on slippery surfaces where drive wheels may lose traction.

Question 23General CDL Knowledge (Oregon CDL Manual core)

What does a flashing red light at a railroad crossing require?

  1. Stop, then proceed only when it is safe Correct answer.
  2. Sound the horn and cross without stopping
  3. Yield to other vehicles and continue
  4. Slow down and proceed if no train is visible

Explanation

A flashing red signal at a railroad crossing requires a complete stop, followed by crossing only when the way is clear. It is not a yield sign. Proceeding without stopping violates the law even if no train is visible.

Question 24General CDL Knowledge (Oregon CDL Manual core)

A driver is transporting a load that extends beyond the rear of the vehicle. What is required?

  1. The load must be removed before driving
  2. Only a warning light on the cab
  3. A red flag or marker at the end of the load during daylight and reflective material at night Correct answer.
  4. No marking is needed if the load is under 4 feet long

Explanation

Loads extending beyond the vehicle must be marked so other drivers can see the overhang. A red flag is used in daylight and reflective material at night. Marking the rear of the load reduces rear-end collisions.

Question 25General CDL Knowledge (Oregon CDL Manual core)

What is the recommended following distance for a commercial vehicle traveling at highway speed in good conditions?

  1. Two seconds regardless of speed
  2. One second for each 10 feet of vehicle length Correct answer.
  3. A fixed 50 feet
  4. One car length for every 10 mph

Explanation

A common rule is one second of following distance for each 10 feet of vehicle length at speeds under 40 mph, with an extra second added at higher speeds. This accounts for the longer stopping distance of heavy vehicles. Fixed distances do not scale with speed or vehicle size.

Question 26General CDL Knowledge (Oregon CDL Manual core)

Before driving, a commercial driver must ensure the vehicle has enough brake system pressure. What is the minimum pressure the air brake system should build to before the vehicle is placed in motion?

  1. 75 psi
  2. 125 psi
  3. 50 psi
  4. 100 psi Correct answer.

Explanation

The Oregon CDL manual directs drivers to let the air system build to at least 100 psi before moving. This ensures adequate reserve pressure for braking and allows the low-pressure warning system to function as designed. A lower reading indicates the compressor or governor may need service.

Question 27General CDL Knowledge (Oregon CDL Manual core)

A driver performs the air brake leakage test by building full pressure, shutting off the engine, and holding the service brake fully applied. How much pressure loss is allowed during one minute for a combination vehicle?

  1. No more than 4 psi
  2. No more than 10 psi
  3. No more than 6 psi
  4. No more than 3 psi Correct answer.

Explanation

With the engine off and the brake released, the system should not lose more than 3 psi in one minute for a combination vehicle; the leak rate with the brake applied is also limited to 3 psi per minute. A larger drop signals a leak that must be repaired before dispatch.

Question 28General CDL Knowledge (Oregon CDL Manual core)

During a pre-trip inspection, a driver finds that the slack adjusters on a drum-brake axle move more than about one inch when pulled by hand. What does this indicate?

  1. That the brake drums are overheated
  2. That the spring brakes are fully released
  3. Excessive pushrod travel that needs repair Correct answer.
  4. Normal adjustment for a loaded trailer

Explanation

Excessive slack adjuster movement means the pushrod travels too far before the brake applies, reducing braking force. The vehicle should be placed out of service until the brakes are adjusted or repaired. Normal pushrod travel is much shorter than one inch of free movement at the slack adjuster.

Question 29General CDL Knowledge (Oregon CDL Manual core)

A driver must back a tractor-trailer around a corner to the left. Which technique gives the best control?

  1. Back toward the driver's side and use the mirrors continuously Correct answer.
  2. Back quickly to reduce the time in the blind area
  3. Back toward the right side to keep the trailer in view
  4. Rely on the trailer's rear camera and skip the mirrors

Explanation

Backing toward the driver's side keeps the trailer visible in the left mirror and allows the driver to correct the path. Backing to the right creates a larger blind area and is avoided when a left-side back is possible. A helper or spotter should be used whenever available.

Question 30General CDL Knowledge (Oregon CDL Manual core)

A commercial driver is about to make a right turn at an intersection. What is the correct way to manage the space to the right of the vehicle?

  1. Swing wide to the left before turning to keep the trailer clear
  2. Accelerate through the turn to reduce time in the intersection
  3. Turn from the left lane to give the trailer more room
  4. Keep the rear wheels close to the curb and watch the right mirror Correct answer.

Explanation

Keeping the rear wheels close to the curb prevents the trailer from cutting the corner and striking the curb or a pedestrian. The driver should check the right mirror throughout the turn. Swinging left is dangerous because it invites traffic to pass on the right.

Question 31General CDL Knowledge (Oregon CDL Manual core)

How should a driver apply the brakes when stopping a commercial vehicle on a dry, level road?

  1. Apply the parking brake to assist the stop
  2. Apply steady pressure and release just before a full stop Correct answer.
  3. Pump the pedal rapidly to prevent lockup
  4. Brake hard and hold until the wheels lock

Explanation

Steady braking with a slight release just before stopping avoids a hard jolt and helps prevent the load from shifting. Pumping the pedal is for older non-ABS systems and is not the normal technique. Locking the wheels reduces steering control.

Question 32General CDL Knowledge (Oregon CDL Manual core)

A driver is descending a long, steep grade with a heavy load. Which combination of controls best keeps the vehicle under control?

  1. The clutch disengaged and the retarder on high
  2. A low gear and intermittent service brake use Correct answer.
  3. A high gear and light continuous braking
  4. Neutral and use the service brakes continuously

Explanation

Selecting a low gear before the descent lets engine braking hold the speed down, and short, firm brake applications keep the drums from overheating. Coasting in neutral is illegal and dangerous because it removes engine braking and control. Continuous light braking can cause brake fade.

Question 33General CDL Knowledge (Oregon CDL Manual core)

What does the term 'off-tracking' describe when a tractor-trailer turns?

  1. The trailer's rear wheels follow a path inside the tractor's front wheels Correct answer.
  2. The steering axle loses contact with the road
  3. The trailer pushes the tractor forward on a downgrade
  4. The front wheels skid outward during a hard turn

Explanation

Off-tracking is the tendency of the rear wheels of a long vehicle to cut inside the path of the front wheels. Drivers must allow extra room at corners and when turning near curbs or other vehicles. The longer the wheelbase, the greater the off-tracking.

Question 34General CDL Knowledge (Oregon CDL Manual core)

A driver must make an emergency stop on a highway shoulder at night. What should the driver do to make the vehicle visible?

  1. Turn off all lights and rely on reflective tape
  2. Place reflective triangles behind the vehicle and use flashers Correct answer.
  3. Leave the headlights on high beam only
  4. Stand behind the trailer with a flashlight

Explanation

Reflective triangles warn approaching traffic, and the four-way flashers make the stopped vehicle more visible. Triangles should be placed behind the vehicle at the required distances. Standing on the roadway is dangerous and does not warn traffic effectively.

Question 35General CDL Knowledge (Oregon CDL Manual core)

When placing warning devices for a stopped commercial vehicle on a divided highway, where should the first triangle be placed?

  1. About 100 feet behind the vehicle
  2. About 40 feet behind the vehicle Correct answer.
  3. About 10 feet behind the vehicle
  4. Directly at the rear bumper

Explanation

On a divided highway the first triangle goes about 10 feet behind the vehicle, with additional triangles placed farther back to give traffic time to react. On a two-lane road the devices are placed farther from the vehicle. Placement should always account for traffic speed and sight distance.

Question 36General CDL Knowledge (Oregon CDL Manual core)

What is the first thing a driver should do when a front tire blows out at highway speed?

  1. Brake hard immediately
  2. Accelerate to regain control
  3. Hold the steering wheel firmly and keep the vehicle straight Correct answer.
  4. Steer sharply onto the shoulder

Explanation

A front tire failure pulls the steering, so the driver must grip the wheel firmly and keep the vehicle moving straight while slowing gradually. Hard braking or sharp steering can cause a loss of control or rollover. The vehicle should be eased off the road once speed is reduced.

Question 37General CDL Knowledge (Oregon CDL Manual core)

A driver's vehicle has anti-lock brakes. What is the correct way to brake during a panic stop?

  1. Pump the brake pedal rapidly
  2. Apply firm, steady pressure and hold it Correct answer.
  3. Release the brake and steer only
  4. Apply the parking brake at the same time

Explanation

With ABS, the driver should press the pedal firmly and hold it; the system modulates pressure to prevent wheel lockup. The pedal may vibrate, which is normal. Pumping the pedal defeats the system and lengthens stopping distance.

Question 38General CDL Knowledge (Oregon CDL Manual core)

What is the correct way to test the service brakes during a pre-trip inspection?

  1. Build pressure, release the parking brake, and apply the service brake while moving slowly Correct answer.
  2. Rev the engine and listen for air leaks
  3. Apply the parking brake and check for movement
  4. Press the pedal with the engine off and hold it for five minutes

Explanation

A service brake test is done by building air pressure, releasing the parking brake, and applying the foot brake at a slow speed to confirm the vehicle stops and does not pull. This checks that the brakes actually function under load. Listening for leaks or holding the pedal with the engine off tests other parts of the system.

Question 39General CDL Knowledge (Oregon CDL Manual core)

A driver is hauling a load of steel coils. What is the most important securement concern?

  1. Preventing the load from shifting forward during braking Correct answer.
  2. Increasing the following distance only
  3. Reducing the vehicle's gross weight
  4. Covering the coils with a tarp

Explanation

Heavy concentrated loads such as steel coils can shift forward under braking and crush the cab or break the securement. They must be blocked and tied down so they cannot move forward, sideways, or rearward. Tying down alone may not be enough without proper blocking.

Question 40General CDL Knowledge (Oregon CDL Manual core)

How many tiedowns are required for a load that is 12 feet long and weighs 8,000 pounds?

  1. Four tiedowns
  2. Three tiedowns
  3. Two tiedowns Correct answer.
  4. One tiedown

Explanation

Cargo longer than 5 feet but not more than 10 feet requires two tiedowns, and loads over 10 feet require at least two tiedowns plus one for each additional 10 feet. A 12-foot load therefore needs a minimum of two tiedowns, with the aggregate working load limit also meeting the weight requirement.

Question 41General CDL Knowledge (Oregon CDL Manual core)

A driver is carrying hazardous materials that require placards. What must the driver do before entering a tunnel?

  1. Check for restrictions and use an alternate route if placarded loads are prohibited Correct answer.
  2. Speed up to clear the tunnel quickly
  3. Sound the horn to warn other drivers
  4. Turn on the hazard flashers and proceed

Explanation

Many tunnels prohibit placarded hazardous materials loads, so the driver must check route restrictions and take an alternate route when required. Ignoring the restriction can result in serious penalties and danger. Hazard flashers do not make a prohibited load legal.

Question 42General CDL Knowledge (Oregon CDL Manual core)

When a driver is involved in a crash involving a hazardous materials release, what should the driver do first?

  1. Try to clean up the spill without protective gear
  2. Continue the trip and report later
  3. Move the vehicle immediately regardless of the spill
  4. Keep people away and notify authorities Correct answer.

Explanation

The driver should keep people away from the release, avoid contact with the material, and notify emergency responders and the carrier. The driver should not attempt cleanup without proper training and equipment. Leaving the scene without reporting is a serious violation.

Question 43General CDL Knowledge (Oregon CDL Manual core)

A driver is driving at night and an oncoming vehicle fails to dim its high beams. What should the driver do?

  1. Turn on high beams to retaliate
  2. Look directly at the oncoming lights
  3. Close one eye until the vehicle passes
  4. Look toward the right edge of the road and slow down Correct answer.

Explanation

Looking toward the right edge of the roadway keeps the driver's vision oriented while avoiding glare from the oncoming lights. Slowing down gives more time to react if the vehicle drifts into the lane. Staring at the lights temporarily blinds the driver.

Question 44General CDL Knowledge (Oregon CDL Manual core)

A commercial driver is driving in heavy fog. Which action is most appropriate?

  1. Follow the vehicle ahead closely for guidance
  2. Slow down and use low beams or fog lights Correct answer.
  3. Stop in the travel lane until the fog clears
  4. Use high beams to see farther

Explanation

Low beams or fog lights reduce glare reflected back by the fog, and slowing down increases reaction time. High beams reflect off the fog and make visibility worse. Following closely or stopping in a travel lane creates a collision hazard.

Question 45General CDL Knowledge (Oregon CDL Manual core)

A driver is driving on an icy road and the rear of the vehicle begins to skid to the left. What should the driver do?

  1. Apply the parking brake
  2. Steer to the right and brake hard
  3. Accelerate to pull the vehicle straight
  4. Turn the steering wheel to the left and ease off the accelerator Correct answer.

Explanation

When the rear skids left, the driver should steer left to align the wheels with the direction of travel and ease off the accelerator. Hard braking or accelerating can worsen the skid. Steering into the skid helps the tires regain traction.

Question 46General CDL Knowledge (Oregon CDL Manual core)

What is the recommended way to check the mirrors while driving a commercial vehicle?

  1. Rely on the rear camera instead
  2. Adjust them while driving
  3. Check them only when changing lanes
  4. Check them regularly and before any maneuver Correct answer.

Explanation

Mirrors should be checked regularly and always before changing lanes, turning, or backing so the driver knows what is alongside and behind. Relying on a camera alone leaves blind spots unmonitored. Mirrors should be adjusted before driving, not while moving.

Question 47General CDL Knowledge (Oregon CDL Manual core)

A driver is driving a vehicle with a high center of gravity and must make a sharp turn. What is the greatest risk?

  1. The steering will lock
  2. The tires will lose air pressure
  3. The vehicle will roll over Correct answer.
  4. The brakes will fail

Explanation

A high center of gravity makes a vehicle more likely to roll over in a sharp turn, especially at speed. The driver should slow down before the turn and avoid sudden steering. Tire pressure, brakes, and steering are separate concerns.

Question 48General CDL Knowledge (Oregon CDL Manual core)

Under Oregon CDL rules, a driver is required to hold a commercial driver license to operate which of the following vehicles in interstate or intrastate commerce?

  1. A single-unit truck with a gross vehicle weight rating of 24,000 pounds
  2. A pickup truck with a gross vehicle weight rating of 9,000 pounds
  3. A passenger van designed to carry 12 people including the driver
  4. A combination vehicle with a gross combination weight rating of 26,001 pounds or more, provided the towed unit exceeds 10,000 pounds Correct answer.

Explanation

A CDL is required for combination vehicles whose gross combination weight rating reaches 26,001 pounds or more when the towed unit exceeds 10,000 pounds. Straight trucks need a CDL only once their GVWR passes 26,000 pounds, and small passenger vans below 16 seats fall outside the CDL classes.

Question 49General CDL Knowledge (Oregon CDL Manual core)

A driver holds a Class B CDL and wants to operate a tractor-trailer combination. What must the driver do?

  1. Pass the Class A knowledge and skills tests and upgrade the license to Class A Correct answer.
  2. Obtain a hazardous materials endorsement before driving any combination
  3. Add a doubles/triples endorsement to the Class B license
  4. Nothing extra, because Class B covers all combination vehicles

Explanation

Class B covers single vehicles over 26,000 pounds and may tow only units of 10,000 pounds or less, so a full tractor-trailer requires a Class A license. The driver must complete the Class A general knowledge test plus the combination vehicle test and skills test.

Question 50General CDL Knowledge (Oregon CDL Manual core)

During a pre-trip inspection, a driver finds that the engine oil pressure gauge reads normal at idle but the oil level on the dipstick is below the add mark. What is the proper action?

  1. Drive the route and check the level again at the next stop
  2. Add oil until the level reaches the full mark before driving Correct answer.
  3. Record the low level on the inspection report and depart
  4. Drain and replace all the oil to reset the level

Explanation

A pre-trip inspection must confirm fluid levels are within the safe operating range, and oil below the add mark must be brought up to full before the vehicle moves. Departing with a known deficiency violates the driver's responsibility to certify the vehicle is in safe condition.