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Arkansas CDL Combination Vehicles Test study materials
Arkansas CDL Combination Vehicles Test study resources

Arkansas CDL Combination Vehicles Test practice questions

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Question 1Driving Combination Vehicles Safely

When you are driving a combination vehicle and the trailer starts to swing out of line, which action is the correct response?

  1. Turn the steering wheel opposite to the trailer's swing
  2. Release the brakes and turn the steering wheel in the direction the trailer is moving Correct answer.
  3. Apply the brakes hard and hold the steering wheel straight
  4. Accelerate sharply to pull the trailer back into line

Explanation

A trailer that swings out of line is usually corrected by releasing the brakes so the wheels can roll and steering in the direction the trailer is moving. Braking hard or accelerating during a swing worsens the loss of control.

Question 2Driving Combination Vehicles Safely

What is the main reason a combination vehicle needs more stopping distance than a single-unit truck?

  1. It has a longer wheelbase
  2. It has greater total weight and more wheels to brake Correct answer.
  3. It carries more cargo weight
  4. It has more air pressure in the system

Explanation

A combination vehicle weighs more overall and must stop more wheels, so it needs more distance to stop. The added weight increases momentum that the brakes must overcome.

Question 3Driving Combination Vehicles Safely

Before backing a tractor-trailer, what should you do first?

  1. Set the trailer brakes only
  2. Turn on the four-way flashers
  3. Get out and walk around to check the path Correct answer.
  4. Sound the horn twice

Explanation

You should get out and inspect the area behind and around the vehicle before backing. Mirrors leave blind spots that a walk-around check catches.

Question 4Driving Combination Vehicles Safely

When coupling a tractor to a trailer, what should you check after the fifth wheel locks?

  1. That the trailer lights are on
  2. That the landing gear is fully raised
  3. That the kingpin is fully seated by pulling the tractor forward gently with the trailer brakes set Correct answer.
  4. That the air lines are connected

Explanation

A pull test with the trailer brakes set confirms the kingpin is locked in the fifth wheel. If the lock is not secure, the tractor will pull out from under the trailer.

Question 5Driving Combination Vehicles Safely

What causes a trailer to swing out of line during a hard stop on a slippery surface?

  1. The fifth wheel being greased
  2. The tractor brakes locking the drive wheels Correct answer.
  3. The trailer being lighter than the tractor
  4. The trailer brakes applying too early

Explanation

If the tractor's drive wheels lock while the trailer wheels keep rolling, the trailer can push the tractor and swing out of line. Balanced braking and avoiding wheel lock help prevent this.

Question 6Driving Combination Vehicles Safely

When should you use the trailer hand valve (trolley valve) while driving?

  1. To make a quick stop in an emergency
  2. To slow the vehicle on long downgrades
  3. To stop the vehicle in normal traffic
  4. To test the trailer brakes only Correct answer.

Explanation

The trailer hand valve is meant only for testing the trailer brakes. Using it while driving can cause the trailer to swing out of line.

Question 7Driving Combination Vehicles Safely

How much space should you leave between your vehicle and the one ahead when driving a combination vehicle at highway speed?

  1. Half the length of your vehicle
  2. At least one second for each ten feet of vehicle length Correct answer.
  3. Two seconds
  4. One second

Explanation

A common rule is one second of following distance for each ten feet of vehicle length at speeds under 40 mph, with more space at higher speeds. Longer combination vehicles need more room to stop.

Question 8Driving Combination Vehicles Safely

What is off-tracking when driving a combination vehicle?

  1. The rear wheels following a shorter path than the front wheels in a turn Correct answer.
  2. The trailer brakes dragging on one side
  3. The trailer lights flashing out of sequence
  4. The tractor drifting sideways on a straight road

Explanation

Off-tracking means the rear wheels of a long vehicle cut inside the path of the front wheels during a turn. You must swing wide enough to keep the trailer wheels from hitting curbs or vehicles.

Question 9Driving Combination Vehicles Safely

When making a right turn in a tractor-trailer, what should you do to avoid hitting the curb with the trailer?

  1. Turn from the left lane and cut sharply
  2. Keep the tractor close to the curb and turn late
  3. Accelerate through the turn to keep the trailer tight
  4. Swing wide to the left before turning right Correct answer.

Explanation

Swinging wide to the left before a right turn gives the trailer room to clear the curb. Turning too tightly causes off-tracking that puts the trailer wheels over the curb.

Question 10Driving Combination Vehicles Safely

What should you do if the trailer breaks away from the tractor?

  1. Apply the tractor brakes hard and steer straight
  2. Pull the trailer hand valve to stop the trailer
  3. Stay off the brake and steer onto the shoulder Correct answer.
  4. Accelerate to catch up to the trailer

Explanation

If the trailer breaks away, keep the tractor under control by staying off the brakes so the wheels can roll and steering to a safe stop. The trailer's emergency line should apply its spring brakes automatically.

Question 11Driving Combination Vehicles Safely

What is the purpose of the emergency air line on a combination vehicle?

  1. To apply the trailer spring brakes if the trailer separates from the tractor Correct answer.
  2. To inflate the trailer tires
  3. To supply air to the trailer brakes during normal driving
  4. To cool the trailer brakes

Explanation

The emergency line carries air that holds the trailer spring brakes released. If the line separates, air escapes and the spring brakes apply automatically.

Question 12Driving Combination Vehicles Safely

When should you test the trailer brakes after coupling?

  1. Only after driving several miles
  2. Only at the end of the trip
  3. Only when the trailer is empty
  4. Before driving, by pulling against the set trailer brakes Correct answer.

Explanation

You should test the trailer brakes before driving by pulling gently against them with the trailer brakes set. This confirms the brakes are working and the coupling is secure.

Question 13Driving Combination Vehicles Safely

What is a jackknife in a combination vehicle?

  1. The trailer wheels locking on wet pavement
  2. The tractor and trailer rolling over on a curve
  3. The trailer pushing the tractor sideways until they fold together Correct answer.
  4. The fifth wheel unlocking during a turn

Explanation

A jackknife happens when the trailer pushes the tractor at an angle until the two units fold together. It often results from locked drive wheels or a trailer swing.

Question 14Driving Combination Vehicles Safely

Which action helps prevent a jackknife when braking on a slippery road?

  1. Braking hard and steering sharply
  2. Using the trailer hand valve
  3. Braking gently and avoiding wheel lock Correct answer.
  4. Shifting to a lower gear while braking hard

Explanation

Gentle braking that avoids locking the wheels keeps the tractor and trailer tracking in line. Locked drive wheels are a common cause of jackknifing.

Question 15Driving Combination Vehicles Safely

How does the height of the fifth wheel affect trailer clearance?

  1. It determines whether the trailer will clear the tractor frame Correct answer.
  2. It changes the trailer lights
  3. It sets the trailer tire pressure
  4. It controls the trailer brake pressure

Explanation

The fifth wheel height must match the trailer so the trailer rides correctly and does not strike the tractor frame. An incorrect height can damage the equipment.

Question 16Driving Combination Vehicles Safely

What should you do before descending a long, steep downgrade in a combination vehicle?

  1. Shift to a lower gear before starting down Correct answer.
  2. Use the trailer hand valve to control speed
  3. Brake hard at the top to slow down
  4. Coast in neutral to save fuel

Explanation

Select a lower gear before the downgrade so engine braking helps control speed. Coasting in neutral or overusing brakes can lead to brake fade.

Question 17Driving Combination Vehicles Safely

What is brake fade?

  1. The brakes getting stronger as they heat up
  2. The air compressor shutting off
  3. The loss of braking power from overheated brakes Correct answer.
  4. The trailer brakes applying too slowly

Explanation

Brake fade is the loss of stopping power that occurs when brakes overheat from prolonged use. Using a lower gear on downgrades helps prevent it.

Question 18Driving Combination Vehicles Safely

When you are being passed by another vehicle while driving a combination vehicle, what should you do?

  1. Sound your horn to warn the driver
  2. Speed up to shorten the pass
  3. Move to the right and maintain your speed Correct answer.
  4. Move to the left to give room

Explanation

Keep your speed steady and stay to the right so the passing vehicle can complete the pass safely. Speeding up lengthens the time the other driver is exposed.

Question 19Driving Combination Vehicles Safely

Why should you avoid sudden lane changes in a combination vehicle?

  1. The air pressure may drop
  2. The cargo may shift forward
  3. The trailer may sway and the vehicle can become unstable Correct answer.
  4. The lights may flicker

Explanation

Sudden steering in a long combination can set the trailer swaying and make the vehicle hard to control. Smooth, gradual lane changes keep the units tracking together.

Question 20Driving Combination Vehicles Safely

What is the correct way to check that the trailer spring brakes apply when the air lines are disconnected?

  1. Check the air gauge for a drop
  2. Listen for the compressor to start
  3. Watch the trailer lights
  4. Watch the trailer wheels for movement while pulling forward Correct answer.

Explanation

With the air lines disconnected, the spring brakes should lock the trailer wheels so the trailer will not roll. Pulling gently against them confirms they are applied.

Question 21Driving Combination Vehicles Safely

When driving a combination vehicle around a curve, what speed adjustment is needed?

  1. Speed up to stabilize the trailer
  2. Brake hard in the middle of the curve
  3. No adjustment is needed
  4. Slow down before the curve Correct answer.

Explanation

A combination vehicle is more likely to roll over in a curve, so you should slow down before entering it. Braking mid-curve can upset the trailer.

Question 22Driving Combination Vehicles Safely

What should you do if the trailer begins to sway while you are driving at highway speed?

  1. Accelerate to pull the trailer straight
  2. Brake hard and turn the wheel
  3. Apply the trailer hand valve
  4. Ease off the accelerator and steer straight Correct answer.

Explanation

Easing off the accelerator and holding the wheel steady lets the sway settle. Hard braking or accelerating can make the sway worse.

Question 23Driving Combination Vehicles Safely

What is the purpose of the glad hands on a combination vehicle?

  1. To hold the kingpin
  2. To connect the air lines between tractor and trailer Correct answer.
  3. To secure the landing gear
  4. To lock the fifth wheel

Explanation

Glad hands are the couplers that join the tractor and trailer air lines. They must be connected properly so the brakes work.

Question 24Driving Combination Vehicles Safely

When you must stop on a railroad crossing in a combination vehicle, what is the safest action?

  1. Get out and check the crossing
  2. Stop on the tracks and wait
  3. Do not stop on the tracks; stop before the crossing Correct answer.
  4. Back up off the tracks

Explanation

You should never stop on railroad tracks because a long combination can be struck by a train. Stop before the crossing and only proceed when you can clear it completely.

Question 25Driving Combination Vehicles Safely

What does the trailer protection valve do if a trailer air line is cut?

  1. It locks the steering
  2. It keeps the trailer brakes released
  3. It applies the trailer spring brakes Correct answer.
  4. It increases engine power

Explanation

When an air line is cut, the protection valve stops air loss and lets the trailer spring brakes apply. This helps bring the trailer to a stop.

Question 26Driving Combination Vehicles Safely

What is the first thing you should do when you are about to drive a combination vehicle and you notice that the trailer has no spring brakes?

  1. Make sure the trailer is loaded evenly.
  2. Check that the emergency air line is connected and the trailer brakes are working. Correct answer.
  3. Inspect the fifth wheel for proper lubrication.
  4. Verify that the trailer lights are functioning.

Explanation

A trailer without spring brakes relies on emergency air pressure to stop if it breaks away. Before driving, you must confirm that the emergency air line is connected and that the trailer brakes apply when the emergency line is disconnected.

Question 27Driving Combination Vehicles Safely

When backing a tractor-trailer, what is the purpose of using the trailer hand valve (trolley valve)?

  1. To increase engine power for backing up.
  2. To lock the trailer brakes and prevent movement.
  3. To control the trailer brakes independently for smoother backing. Correct answer.
  4. To release the trailer spring brakes.

Explanation

The trailer hand valve allows you to apply the trailer brakes separately from the tractor brakes, which can help control the trailer during backing maneuvers. It is not used to lock the brakes completely or to release spring brakes.

Question 28Driving Combination Vehicles Safely

What is the proper way to test the trailer service brakes after coupling to a trailer?

  1. With the air system charged, push the brake pedal and check for air loss. Correct answer.
  2. Set the parking brake and rev the engine.
  3. Disconnect the emergency line and listen for air escape.
  4. Pull the tractor ahead slowly and apply the trailer hand valve.

Explanation

To test the trailer service brakes, the air system must be fully charged. Then, with the engine running, push the brake pedal and watch for a drop in air pressure, which indicates the trailer brakes are applying. This ensures the service line and brakes are functioning.

Question 29Driving Combination Vehicles Safely

When driving a combination vehicle, what is the effect of a light load on the trailer?

  1. It can cause the trailer wheels to lock up more easily during braking. Correct answer.
  2. It improves traction and reduces stopping distance.
  3. It has no effect on braking or stability.
  4. It increases the risk of the trailer swaying.

Explanation

A light load reduces the weight on the trailer tires, which can cause them to lock up more easily during braking. This can lead to skidding and loss of control, especially on slippery surfaces.

Question 30Driving Combination Vehicles Safely

What is the safest way to handle a combination vehicle when driving on a road with a steep downgrade and sharp curves?

  1. Apply the brakes continuously to maintain a slow speed.
  2. Coast in neutral to save fuel.
  3. Use the trailer hand valve to control speed.
  4. Shift to a lower gear and use the brakes sparingly. Correct answer.

Explanation

On a steep downgrade with curves, you should shift to a lower gear before starting down and use the brakes sparingly to avoid overheating. This approach helps maintain control and prevents brake fade.

Question 31Air Brakes and Brake Systems on Combination Vehicles

On a combination vehicle with air brakes, what is the first thing that happens when you press the brake pedal?

  1. An electrical signal engages the trailer relay valve
  2. Air pressure is released from the brake chambers Correct answer.
  3. The spring brakes are mechanically released
  4. The compressor begins building pressure in the tanks

Explanation

Pressing the foot valve meters compressed air out of the supply tanks and toward the brake chambers, where it pushes the pushrod to apply the brakes. The compressor runs continuously to maintain tank pressure and is not triggered by the pedal. The system is pneumatic, not electrical, and spring brakes release when air pressure is applied, not when you brake.

Question 32Air Brakes and Brake Systems on Combination Vehicles

What is the purpose of the trailer relay valve?

  1. It automatically sets the trailer spring brakes when parked
  2. It limits trailer tank pressure to 60 psi
  3. It speeds up brake application and release at the trailer wheels Correct answer.
  4. It filters moisture out of the trailer air supply

Explanation

The relay valve uses a small control signal from the tractor to send a large volume of air from the trailer tank directly to the trailer brake chambers. This shortens the distance the air must travel, so trailer brakes apply and release faster. Moisture removal is the job of the air dryer, and spring brake parking is controlled by the parking valve.

Question 33Air Brakes and Brake Systems on Combination Vehicles

During a pre-trip inspection you find the air pressure builds from 85 to 100 psi in about 45 seconds at normal engine speed. What does this indicate?

  1. The compressor is building pressure too slowly Correct answer.
  2. The air dryer is bypassing
  3. The governor is cutting out too early
  4. The system is building pressure faster than required

Explanation

The standard is that pressure should build from 85 to 100 psi within about 45 seconds at normal operating rpm; taking longer than that points to a weak compressor, a leak, or a restricted intake. A properly working system reaches the range within the limit. Early governor cut-out and dryer bypass would not slow the build in this way.

Question 34Air Brakes and Brake Systems on Combination Vehicles

With the engine off and the system fully charged, you hold the brake pedal down and the air pressure drops steadily. What is the most likely meaning?

  1. The spring brakes are applying normally
  2. The governor is stuck in the cut-in position
  3. There is an air leak somewhere in the brake system Correct answer.
  4. The low pressure warning system is faulty

Explanation

A static system with the pedal applied should hold pressure with only a small loss. A steady, continuing drop means air is escaping through a leak in a line, fitting, chamber, or valve. The warning system and governor do not cause pressure loss with the engine off.

Question 35Air Brakes and Brake Systems on Combination Vehicles

What is the function of the tractor protection valve?

  1. It regulates the pressure sent to the trailer brakes
  2. It closes the tractor air lines when pressure drops too low or the lines separate Correct answer.
  3. It balances air pressure between the primary and secondary circuits
  4. It prevents the trailer from rolling when the parking brake is set

Explanation

The tractor protection valve senses supply pressure and, when it falls below a safe level or the trailer lines separate, closes off the tractor's air so the tractor retains enough pressure to stop. It also signals the trailer emergency system to apply the trailer spring brakes. It does not regulate normal trailer brake pressure or balance the two service circuits.

Question 36Air Brakes and Brake Systems on Combination Vehicles

The low air pressure warning on your combination vehicle must activate before pressure drops below what level?

  1. 30 psi
  2. 45 psi
  3. 60 psi Correct answer.
  4. 80 psi

Explanation

The warning buzzer and light must come on before the pressure in the tanks falls below 60 psi, giving the driver time to stop safely before spring brakes apply. The spring brakes begin to apply automatically at a much lower pressure, around 20 to 45 psi.

Question 37Air Brakes and Brake Systems on Combination Vehicles

You are driving a combination vehicle when the low pressure warning sounds and the buzzer continues. What should you do?

  1. Stop as soon as it is safe and find out why pressure is low Correct answer.
  2. Shift to a lower gear and continue to the nearest stop
  3. Release the parking brake to restore air flow
  4. Pump the brake pedal to rebuild pressure

Explanation

A low pressure warning means the system may soon lose enough air to apply the spring brakes, so you should stop in a safe place and identify the cause before continuing. Pumping the pedal uses more air and makes the loss worse. Continuing to drive risks a sudden automatic brake application.

Question 38Air Brakes and Brake Systems on Combination Vehicles

How do you test that the trailer spring brakes will apply if the air lines separate from the tractor?

  1. Charge the system, then press the foot valve and hold it
  2. Charge the system, then fan the brake pedal several times
  3. Charge the system, then shut off the engine and watch the gauge
  4. Charge the system, then pull the trailer air supply valve out and listen for the brakes to set Correct answer.

Explanation

Pulling the trailer air supply (emergency) valve out simulates a loss of supply air to the trailer, which should cause the trailer spring brakes to apply. This checks the emergency relay and spring brake function. Fanning the pedal checks service brakes and leak rate, not the emergency spring brake function.

Question 39Air Brakes and Brake Systems on Combination Vehicles

What is a dual air brake system?

  1. A system that uses both air and hydraulic pressure
  2. A system where the trailer has its own independent compressor
  3. Two separate air systems, each with its own tanks, that operate different brake circuits Correct answer.
  4. A system with two compressors that alternate duty

Explanation

A dual air brake system has two separate circuits, typically primary and secondary, each with its own reservoir, so a failure in one circuit still leaves braking ability in the other. It is not two compressors, a trailer-mounted compressor, or a mixed air-hydraulic design.

Question 40Air Brakes and Brake Systems on Combination Vehicles

During a pre-trip inspection, why should you drain the air tanks?

  1. To reset the low pressure warning switch
  2. To lower the system pressure before adjusting the governor
  3. To check that the compressor is working
  4. To remove moisture and oil that can damage valves and freeze in cold weather Correct answer.

Explanation

Compressed air carries water vapor and oil that condense in the tanks; draining removes this contamination so it does not corrode or clog valves and does not freeze in lines during cold weather. Draining is not used to adjust the governor, reset a switch, or test the compressor.

Question 41Air Brakes and Brake Systems on Combination Vehicles

You are coupling a tractor to a trailer. When should you supply air to the trailer?

  1. After the trailer is secured and the landing gear is raised
  2. As soon as the kingpin is locked
  3. After connecting the glad hands and opening the shut-off valves Correct answer.
  4. Before backing under the trailer

Explanation

Air is supplied to the trailer only after the glad hands are connected and the trailer shut-off valves are opened, which charges the trailer tanks and releases the trailer spring brakes. Supplying air before coupling or before the lines are connected can cause the trailer to move unexpectedly.

Question 42Air Brakes and Brake Systems on Combination Vehicles

What color are the two trailer air line glad hands normally, and which carries the emergency supply?

  1. Green is service, black is emergency supply
  2. Both are black and interchangeable
  3. Red is service, blue is emergency supply
  4. Blue is service, red is emergency supply Correct answer.

Explanation

The blue line is the service line that carries brake application signals, and the red line is the emergency line that supplies air to charge the trailer tanks and hold off the spring brakes. The couplers are keyed differently so they cannot be crossed.

Question 43Air Brakes and Brake Systems on Combination Vehicles

You accidentally cross the trailer air lines when coupling. What is likely to happen?

  1. The trailer spring brakes will not release and the trailer may not move Correct answer.
  2. The trailer service brakes will not release
  3. The trailer brakes will apply and release normally
  4. The tractor parking brake will not set

Explanation

If the lines are crossed, supply air goes to the service line instead of the emergency line, so the trailer tanks do not charge and the spring brakes stay applied. The trailer will not roll until the lines are corrected. The keyed couplers make this unlikely but possible with adapters or damaged fittings.

Question 44Air Brakes and Brake Systems on Combination Vehicles

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

  1. Fan the pedal five times and watch the gauge
  2. Set the parking brake and accelerate against it
  3. Move forward slowly and apply the brakes normally, checking that the combination stops Correct answer.
  4. Move forward slowly and apply the brakes with the trailer air supply valve pulled out

Explanation

A service brake test is done by moving slowly and applying the brakes normally to confirm the combination slows and stops without pulling or delay. Pulling the trailer air supply valve tests emergency spring brake application, not normal service braking. Fanning the pedal tests leaks, and accelerating against the parking brake tests holding power.

Question 45Air Brakes and Brake Systems on Combination Vehicles

Why does a combination vehicle with air brakes need a longer stopping distance than a similar single vehicle?

  1. The compressor cannot keep up with demand
  2. The combination weighs less per axle
  3. The trailer brakes are weaker than tractor brakes
  4. Air takes time to travel through longer lines, delaying trailer brake application Correct answer.

Explanation

Because the trailer is far from the foot valve, air must travel through longer lines, so trailer brakes apply slightly after the tractor brakes. This lag adds to stopping distance and is why you should leave more following distance. Trailer brakes are not inherently weaker, and axle loading does not explain the lag.

Question 46Air Brakes and Brake Systems on Combination Vehicles

What is the purpose of the spring brakes on a combination vehicle?

  1. To balance braking between tractor and trailer
  2. To release the trailer when the glad hands are disconnected
  3. To apply automatically when air pressure is lost and to serve as a parking brake Correct answer.
  4. To provide normal service braking

Explanation

Spring brakes are held off by air pressure and apply by spring force when pressure is lost, so they function as an automatic emergency and parking brake. They are not used for normal service braking, which is done by air applied to the service chambers.

Question 47Air Brakes and Brake Systems on Combination Vehicles

You must never do which of the following when working under a combination vehicle with air brakes?

  1. Rely on air pressure alone to hold the spring brakes off Correct answer.
  2. Drain the air tanks before inspection
  3. Use wheel chocks in addition to the parking brake
  4. Block the wheels before releasing the parking brake

Explanation

If air pressure is the only thing holding the spring brakes off and that pressure is lost, the brakes can release and the vehicle can roll. Always secure the vehicle mechanically with chocks and follow the manufacturer's procedure before working underneath. Draining tanks and using chocks are safe practices.

Question 48Air Brakes and Brake Systems on Combination Vehicles

The air compressor on your tractor is driven by what?

  1. An electric motor
  2. The trailer axle
  3. The engine Correct answer.
  4. A hydraulic pump

Explanation

The air compressor is mounted on and driven by the engine, usually through a belt or gear drive, so it only builds air while the engine runs. It is not electrically or hydraulically driven, and the trailer has no role in driving it.

Question 49Air Brakes and Brake Systems on Combination Vehicles

What does the governor do in an air brake system?

  1. It shuts off the engine if pressure is too low
  2. It regulates the pressure applied to the trailer brakes
  3. It limits vehicle speed on downgrades
  4. It controls when the compressor cuts in and out to maintain tank pressure Correct answer.

Explanation

The governor senses tank pressure and turns the compressor's pumping action on (cut-in) and off (cut-out) to keep pressure within the proper operating range. It does not meter trailer brake pressure, control road speed, or shut down the engine.

Question 50Air Brakes and Brake Systems on Combination Vehicles

You are descending a long, steep grade with a loaded combination vehicle. What is the correct braking technique?

  1. Use a low gear and apply the brakes firmly enough to slow, then release and repeat Correct answer.
  2. Shift to neutral and rely on the brakes
  3. Hold steady light pressure on the brake pedal all the way down
  4. Apply the trailer hand valve to control speed

Explanation

On a long downgrade you should select a low gear and use controlled, firm brake applications followed by release so the brakes have time to cool. Light continuous pressure overheats the brakes, and the trailer hand valve should not be used for routine speed control.