CSLB General Building (B) — All Questions

Before backing a tractor under a trailer, where should the trailer be positioned relative to the fifth wheel?

• a.Slightly higher than the fifth wheel so it can slide up as you back
• b.Low enough that the trailer is raised slightly by the tractor as you back under it✓
• c.At the exact same height so no lifting occurs
• d.Below the frame rails so the kingpin drops in freely

The trailer should be low enough that it is raised slightly when the tractor backs under it. This ensures the fifth wheel makes solid contact and the kingpin seats properly. If the trailer is too low the tractor may hit and damage the nose; too high and it can miss the fifth wheel.

What is the correct order for positioning the tractor before coupling to a trailer?

• a.Line the tractor directly in front of the trailer, never backing under it at an angle✓
• b.Approach from the side to save time
• c.Back in from a 45-degree angle for better vision
• d.Position the tractor with the fifth wheel already tilted forward

You should line the tractor up directly in front of the trailer and never back under at an angle. Backing under at an angle can push the trailer sideways and break the landing gear. Approaching straight also helps the kingpin center in the fifth wheel jaws.

Before backing under a trailer, the fifth wheel should be tilted how?

• a.Tilted down toward the rear of the tractor
• b.Kept perfectly level
• c.Tilted down toward the rear so the kingpin can rise into the jaws✓
• d.Locked flat with jaws already closed

The fifth wheel should be tilted down toward the rear of the tractor so the kingpin can slide up the ramp and into the locking jaws. The jaws must be open before backing under. A properly tilted fifth wheel allows smooth coupling and correct kingpin seating.

When connecting the glad hands, what must you check to avoid a dangerous coupling mistake?

• a.That both hoses are the same color
• b.That the hoses are as short as possible
• c.That the tractor engine is running
• d.That the emergency (red) and service (blue) lines are connected to the correct couplers, not crossed✓

You must make sure the emergency and service air lines are connected to the correct glad hands and not crossed. Crossing the lines can leave the trailer with no emergency brake protection. Many rigs color-code red for emergency and blue for service to prevent mistakes.

After the kingpin has locked into the fifth wheel, how should you test that the coupling is secure?

• a.Put the tractor in low gear and gently pull forward against the locked trailer brakes (tug test)✓
• b.Rev the engine while in neutral
• c.Bounce the cab up and down
• d.Release all air and roll forward

You should perform a tug test by putting the tractor in low gear and gently pulling forward while the trailer brakes are locked. If the coupling is secure, the trailer will not separate. This confirms the kingpin is fully engaged before you crawl under to inspect.

After the tug test, why should you go under the trailer and look into the back of the fifth wheel?

• a.To check the color of the kingpin
• b.To confirm the fifth wheel jaws have closed around the shank of the kingpin✓
• c.To measure the height of the landing gear
• d.To grease the fifth wheel plate

You should go under the trailer with a flashlight and look at the back of the fifth wheel to confirm the locking jaws have closed completely around the shank, not the head, of the kingpin. This visual check catches a false coupling that the tug test alone might miss. A gap means the coupling is not safe.

When should the locking jaws be closed around the kingpin?

• a.Around the top head of the kingpin
• b.Loosely, so the trailer can pivot freely
• c.Around the shank of the kingpin, with no gap between the upper and lower fifth wheel plates✓
• d.Only after the landing gear is fully lowered

The locking jaws must close around the shank of the kingpin, and there should be no space between the upper and lower fifth wheel plates. If the jaws close on the head of the kingpin, the coupling can come apart. A gap between the plates indicates a bad coupling that must be corrected before driving.

After the trailer is securely coupled and supported by the tractor, what should you do with the landing gear?

• a.Leave it partway down for extra support
• b.Raise it only halfway
• c.Leave it fully down until you reach the destination
• d.Raise it fully and secure the crank handle✓

Once the trailer weight rests on the tractor, raise the landing gear all the way up and secure the crank handle in its holder. Landing gear left partway down can catch on railroad tracks or uneven surfaces. A loose crank handle can strike someone or damage equipment.

Before supplying air to the trailer, why should you check the trailer brakes are set?

• a.To keep the trailer from moving when the tractor backs under it or when air is applied✓
• b.To warm up the brake shoes
• c.To test the ABS light
• d.To release the parking brake automatically

You should ensure the trailer brakes are locked, either with wheel chocks or by having air already in the system, so the trailer cannot move while coupling. A trailer that rolls during coupling can cause serious injury or damage. Chock the wheels if you are not sure the spring brakes will hold.

When you push the trailer air supply valve in (supply air to trailer), what should happen?

• a.The trailer parking brakes stay locked
• b.Air flows to the trailer and the trailer spring brakes release✓
• c.The tractor engine shuts off
• d.The fifth wheel unlocks

Pushing in the trailer air supply valve sends air to the trailer, which releases the trailer spring (parking) brakes. You should always charge the trailer air and then test the brakes before moving. This step is done after confirming the air lines are connected correctly.

During uncoupling, when should you lower the landing gear?

• a.After pulling the tractor completely out
• b.Only if the trailer is empty
• c.Before releasing the fifth wheel locking jaws, until it makes firm contact with the ground✓
• d.At the same time you pull the fifth wheel release handle

You should lower the landing gear until it makes firm contact with the ground before unlocking the fifth wheel. If the trailer is loaded, turn the crank a few extra times to lift some weight off the tractor. This prevents the trailer from dropping suddenly when the tractor pulls out.

What should you do with the air lines and electrical cord before pulling the tractor away from the trailer during uncoupling?

• a.Leave them connected and let them stretch off
• b.Cut them if they are stuck
• c.Wrap them around the kingpin
• d.Disconnect them and hang or store them so they will not be crushed or dragged✓

Before pulling the tractor clear, disconnect the air lines and electrical cord and secure them so they are not damaged. Hang the glad hands on dummy couplers or dead-end them to keep dirt out. Leaving lines connected can tear them apart when the tractor drives away.

When uncoupling, what does pulling the fifth wheel release handle to the open position do?

• a.Unlocks the fifth wheel locking jaws so the kingpin can slide out✓
• b.Raises the landing gear
• c.Supplies air to the trailer
• d.Locks the trailer brakes

Pulling the release handle to the open position unlocks the fifth wheel jaws so the trailer kingpin can separate as the tractor pulls forward. You should only do this after the landing gear supports the trailer and the trailer brakes are set. Chock the wheels if the trailer has no spring brakes.

After unlocking the fifth wheel jaws during uncoupling, how should you move the tractor?

• a.Pull forward quickly to clear the area
• b.Ease the tractor forward until the fifth wheel comes out from under the trailer, then stop✓
• c.Back up sharply to free the kingpin
• d.Turn hard while pulling out

You should ease the tractor forward slowly until the fifth wheel comes out from under the trailer apron, then stop with the tractor frame still under the trailer. This keeps the trailer supported while you disconnect lines. Pulling out too far or too fast before the trailer is fully supported can drop the trailer.

Why is it important that the kingpin be properly locked, not just resting on the closed fifth wheel jaws?

• a.To reduce fuel use
• b.To keep the fifth wheel greased
• c.Because a kingpin resting on top of the closed jaws (a false coupling) can slip out and separate the trailer✓
• d.Because it makes turning easier

A false coupling occurs when the fifth wheel jaws close but the kingpin is sitting on top of them rather than locked around the shank. This looks connected but can separate under load or over bumps, dropping the trailer. That is why the tug test and the visual under-trailer check are both required.

When raising the landing gear after coupling, what should you be aware of regarding the crank handle?

• a.It should be left extended for balance
• b.It cannot be secured
• c.It should spin freely while driving
• d.It must be secured in its holder so it does not swing out or get caught✓

After fully raising the landing gear, the crank handle must be secured in its holder. An unsecured handle can swing out and strike people, other vehicles, or catch on obstacles. Always confirm the gear is fully up and the handle is stowed before moving.

Why should you use two low-pressure gears when starting to raise loaded landing gear rather than high gear?

• a.Low gear makes cranking easier and reduces the risk of injury when lifting heavy loads✓
• b.High gear is faster and always preferred
• c.Low gear damages the crank
• d.Landing gear has only one gear

Many landing gear cranks have a low and a high gear. Use the low gear to start raising a heavy load because it takes less effort, then switch to high gear once the weight is off. Trying to crank a heavy load in high gear can strain the mechanism and cause injury.

What should you check about the fifth wheel plate before backing under a trailer?

• a.That it is painted the correct color
• b.That it is properly greased to prevent steering problems and reduce friction✓
• c.That it is completely dry
• d.That the jaws are already closed

The fifth wheel plate should be properly lubricated with grease to reduce friction between the trailer and tractor. A dry fifth wheel can cause steering problems and hard, jerky turning. You should also confirm the jaws are open and the fifth wheel is tilted down before backing under.

Before coupling, why should you inspect the area around and under the trailer?

• a.To count the tires
• b.To look for a place to park the tractor
• c.To check for people, obstacles, or objects and confirm the trailer wheels are chocked or brakes set✓
• d.To adjust the mirrors

You should walk around and check under the trailer for people, pets, or obstacles before backing under it. Confirm the trailer wheels are chocked or the trailer brakes are set so it cannot move. This inspection prevents injury and equipment damage during coupling.

Which of the following is the correct sequence when coupling a tractor and trailer?

• a.Raise landing gear, then back under, then connect air lines
• b.Connect air lines, then tug test, then position tractor
• c.Back under, raise landing gear, then set trailer height
• d.Inspect and prepare, back under and couple, connect air lines and supply air, test coupling, raise landing gear✓

The proper sequence is to inspect and prepare the equipment, back under and couple, connect and supply air lines, test the coupling with a tug test and visual check, then raise the landing gear. Following the correct order prevents a false coupling and dropped trailer. Skipping steps like the air connection or tug test is dangerous.

What is the purpose of the safety catch on many fifth wheel release levers?

• a.It must be released before the fifth wheel handle can be pulled to unlock, preventing accidental uncoupling✓
• b.It greases the fifth wheel automatically
• c.It holds the trailer brakes on
• d.It raises the landing gear

Many fifth wheels have a safety catch over the release lever that must be moved before the handle can be pulled. This prevents the fifth wheel from unlocking accidentally while driving. You release the catch only when you intend to uncouple.

If the trailer is too low when you back under it, what is the likely result?

• a.The kingpin locks perfectly
• b.The tractor may strike and damage the nose of the trailer instead of coupling✓
• c.The landing gear rises automatically
• d.The glad hands connect themselves

If the trailer is set too low, the tractor frame or fifth wheel can hit and damage the front of the trailer rather than sliding underneath. If it is too high, the tractor may pass under without the kingpin engaging the fifth wheel. The trailer should be just low enough to be lifted slightly during coupling.

Why must you supply air to the trailer and check for air leaks before moving after coupling?

• a.To cool the engine
• b.To inflate the tires
• c.To confirm the trailer brakes work and the air system holds pressure before driving✓
• d.To lower the landing gear

After connecting the air lines you must supply air to the trailer and check that the system holds pressure and the trailer brakes operate. Listening for leaks and watching the gauge confirms the braking system is sealed. Driving with a leaking or unconnected trailer air line can leave you without trailer brakes.

When should you chock the trailer wheels during coupling or uncoupling?

• a.Never, the fifth wheel holds the trailer
• b.Only on flat ground
• c.Only when the tractor is attached
• d.When you are not sure the trailer spring brakes will hold it, such as an empty or brakeless trailer✓

You should chock the trailer wheels whenever you are unsure the trailer will stay in place, such as a trailer without spring brakes or one parked on a slope. Chocks keep the trailer from rolling during coupling or uncoupling. This protects you from a runaway trailer while you work between the units.

When inspecting the coupling system of a combination vehicle, what should you check about the fifth wheel mounting?

• a.That mounting bolts and brackets are secure and none are missing or broken✓
• b.That it is painted to match the cab
• c.That the fifth wheel is completely dry
• d.That it is tilted forward

During inspection you must check that the fifth wheel is securely mounted, with no missing or broken mounting bolts, brackets, or welds. A loose or cracked fifth wheel mount can fail under load. This is a critical part of the combination vehicle coupling inspection.

What are you checking for when you inspect the trailer air lines (glad hands) during a pre-trip?

• a.Only their color
• b.That they are not cut, cracked, worn, or leaking, and are properly connected and secured✓
• c.That they are wrapped around the frame
• d.That they are as long as possible

You should inspect the air lines for cuts, cracks, wear, or leaks, and make sure they are securely connected and not dragging or tangled. Damaged air lines can cause a loss of braking. Properly supported lines also avoid chafing against the frame.

When inspecting the kingpin and fifth wheel coupling, what condition indicates a problem?

• a.A greased fifth wheel plate
• b.Locking jaws closed around the kingpin shank
• c.A visible gap between the upper and lower fifth wheel plates✓
• d.The safety catch engaged over the release lever

A gap between the upper and lower fifth wheel plates indicates an improper coupling that could fail. There should be no space between the plates and the locking jaws should be closed around the shank. Finding a gap means you must recouple before driving.

During a combination vehicle inspection, what should you check about the landing gear?

• a.That it is greased and turning
• b.That it is halfway down
• c.That the crank spins freely
• d.That it is fully raised, the crank handle is secured, and no parts are missing, damaged, or bent✓

You should confirm the landing gear is fully raised, the crank handle is secured in place, and there are no missing, bent, or damaged parts. Landing gear that is not fully up can catch on obstacles or railroad crossings. Damaged legs may collapse when supporting the trailer.

When inspecting the electrical connection between tractor and trailer, what should you verify?

• a.That the electrical cord is firmly plugged in, secured, and not damaged or dragging✓
• b.That the cord is unplugged for safety
• c.That the cord matches the paint color
• d.That the cord is wrapped around the kingpin

You should verify the electrical (light) cord is firmly seated in its socket, secured with the safety latch if equipped, and free of cuts or fraying. A loose or damaged cord can cause the trailer lights to fail. It should also be routed so it does not drag or chafe.

How can you test whether the trailer emergency brakes work during an inspection?

• a.By revving the engine in neutral
• b.By charging the trailer air, shutting off the tractor engine, then pulling the trailer air supply valve out and checking the trailer brakes apply✓
• c.By bouncing the trailer
• d.By disconnecting the light cord

To test the trailer emergency (spring) brakes, charge the air system, then pull out the trailer air supply valve (or let air bleed) and confirm the trailer spring brakes set. You can then apply the tractor gently in low gear to confirm the trailer stays put. This verifies the emergency braking function before driving.

When checking the trailer service brakes during a combination vehicle inspection, what should you do?

• a.Only look at the brake lights
• b.Rev the engine and listen
• c.Charge the system, release the parking brakes, move slowly, and apply the brake pedal to confirm the vehicle stops and does not pull to one side✓
• d.Disconnect the glad hands

To check service brakes, charge the air system, release the parking brakes, roll forward slowly, and press the brake pedal. The vehicle should stop straight without pulling to one side and without unusual feel. Pulling or a delayed stop can indicate a brake problem on the tractor or trailer.

What should you inspect on the trailer's tires and wheels during a pre-trip?

• a.Only the color of the rims
• b.Only the front tires
• c.That the tires are the newest brand
• d.That tires have proper inflation and tread, no cuts or bulges, and wheels have no missing, loose, or damaged lug nuts or cracks✓

You should inspect all trailer tires for proper inflation, adequate tread depth, and freedom from cuts, bulges, or uneven wear. Wheels and rims must have no cracks, and lug nuts must be present and tight with no rust streaks indicating looseness. Trailer tires are easy to overlook but critical to safety.

Why should you check the air line connections between the tractor and trailer for leaks?

• a.Because leaking air lines can cause loss of braking ability in the combination vehicle✓
• b.Because leaks make the horn quieter
• c.Because leaks change the tire pressure
• d.Because leaks affect the paint

Air line leaks reduce the air pressure available for braking and can lead to brake failure. You should listen and feel for leaks at the glad hand connections and along the hoses during inspection. Any significant leak must be repaired before driving.

When inspecting a combination vehicle, why must you check that the trailer is not overloaded or unbalanced?

• a.Because overloading changes the paint color
• b.Because improper weight distribution affects braking, handling, and can raise the center of gravity and rollover risk✓
• c.Because it changes the trailer length
• d.Because it lowers the landing gear

An overloaded or poorly balanced trailer affects braking distance, steering, and stability. Loads that are too high or shifted raise the center of gravity and increase rollover risk. Confirming proper weight and secure cargo is part of a safe combination vehicle inspection.

What should you look for when inspecting the sliding fifth wheel (if equipped)?

• a.That it is welded solid
• b.That it slides freely while driving
• c.That the slide is locked in place and the locking pins are fully engaged✓
• d.That it is removed

On a sliding fifth wheel you must confirm the slide is locked in position and the locking pins are fully engaged, not just resting. An unlocked slide can move under braking and shift weight or cause a coupling failure. Also check that the slide rails and stops are not cracked or worn.

During the walk-around inspection of a trailer, what should you check about the trailer lights and reflectors?

• a.Only that the headlights work
• b.Only that reflectors are shiny
• c.That the trailer has no lights
• d.That all required clearance, marker, brake, tail, and turn lights work and reflectors are present and clean✓

You should confirm all required trailer lights, including clearance, marker, brake, tail, and turn signals, are working, and that reflectors are present and clean. Trailer lights make the rig visible to other drivers, especially at night. Burned-out lights or missing reflectors are common violations.

When inspecting the trailer's suspension system, what should you look for?

• a.Cracked or broken spring hangers, missing or broken leaves, and loose or damaged air suspension parts✓
• b.Only the tire pressure
• c.Only the mud flaps
• d.The color of the frame

You should inspect the trailer suspension for cracked or broken spring hangers, missing or shifted spring leaves, and any loose or leaking air suspension components. Suspension failures can affect handling and load stability. Also check U-bolts, shock absorbers, and mounting hardware.

What is the purpose of checking the trailer's air tank drain and slack adjusters during inspection?

• a.To confirm the tank is painted
• b.To ensure the brakes are properly adjusted and moisture is drained so brakes work reliably✓
• c.To check the trailer length
• d.To grease the kingpin

Draining the trailer air tank removes moisture and oil that can damage the system, and checking slack adjusters confirms the brakes are within proper adjustment. Out-of-adjustment brakes reduce stopping power. These checks help ensure the trailer brakes perform correctly.

Why should you check that the trailer doors, cargo securement, and header board are secure during inspection?

• a.To improve fuel economy
• b.To make the trailer lighter
• c.So cargo cannot shift or fall out and doors stay latched while driving✓
• d.To change the trailer color

You should confirm trailer doors are securely latched and cargo is properly secured so nothing shifts or falls during transit. A shifting load affects handling and can raise rollover risk, while an unlatched door can release cargo onto the road. Securement devices, tie-downs, and the header board should be checked.

When performing an air brake check on a combination vehicle, why do you test the tractor protection valve and trailer air supply valve?

• a.To grease the valves
• b.To change gear ratios
• c.To check the paint
• d.To confirm that if trailer air pressure drops too low, the valves close and protect the tractor's air supply✓

The tractor protection valve and trailer air supply valve are tested to confirm they will close automatically when air pressure drops to a low level, typically between 20 and 45 psi. This protects the tractor's braking system if a trailer air line breaks. Confirming this function is a key part of the combination air brake check.

What should you check about the mounting of the fifth wheel skid plate and the trailer apron?

• a.That the trailer apron sits flat on the fifth wheel and there is no gap or damage to the plates✓
• b.That the apron is removed
• c.That the plate is unpainted
• d.That the apron is loose for flexibility

You should confirm the trailer apron rests flat and fully on the fifth wheel skid plate with no gap or bending. Damage or a gap indicates a bad coupling or worn parts that could fail. The plates must contact firmly for a safe, stable connection.

During inspection, what should you check about the trailer's mud flaps and rear-end protection (ICC bumper)?

• a.Only their color
• b.That they are present, securely mounted, and not damaged or missing✓
• c.That they drag on the ground
• d.That they are removed to reduce weight

You should verify the mud flaps and rear impact guard (ICC/DOT bumper) are present, securely mounted, and undamaged. Mud flaps reduce spray to other vehicles, and the rear guard helps prevent underride in a collision. Missing or broken components are violations.

When you check air lines during a combination inspection, which lines are you connecting and inspecting?

• a.Only the fuel line
• b.Only the electrical line
• c.The service (blue) air line and the emergency (red) air line✓
• d.The coolant and oil lines

On a combination vehicle you inspect and connect the service air line, often blue, and the emergency air line, often red. The service line carries air for normal braking, and the emergency line supplies the trailer reservoir and controls the spring brakes. Both must be secure and leak-free.

Why is it important to check the trailer registration, load limits, and that the trailer is not leaking (for tankers or vans) during inspection?

• a.To increase speed
• b.To reduce the number of tires
• c.To change the fifth wheel
• d.To ensure the vehicle is legal, safely loaded, and not spilling cargo or fluids on the road✓

You should confirm the trailer paperwork is in order, the load is within weight limits, and there are no leaks from the cargo or vehicle systems. Overweight or leaking trailers are illegal and dangerous. These checks keep the rig compliant and prevent hazards to other road users.

What is off-tracking (or cheating) in a combination vehicle?

• a.The rear wheels follow a shorter path than the front wheels when turning, tracking inside the turn✓
• b.The trailer swings wider than the tractor
• c.The tires lose air pressure
• d.The trailer brakes lock up

Off-tracking is when the rear trailer wheels follow a shorter, inside path compared to the front wheels during a turn. The longer the vehicle, the more the rear wheels off-track. Drivers must swing wider and steer the front of the tractor farther out so the trailer wheels clear curbs and obstacles.

To make a right turn with a combination vehicle and avoid the trailer wheels hitting the curb, you should:

• a.Turn sharply and early from the left lane
• b.Turn wide as you complete the turn, keeping the rear of your vehicle close to the curb✓
• c.Swing wide to the left before starting the turn so others can pass on the right
• d.Speed up through the turn

You should turn wide as you complete the turn, not before it, keeping the rear of your vehicle close to the curb. Swinging wide to the left first invites other drivers to pass on your right, where they can be crushed as the trailer completes the turn. Because of off-tracking, you must keep the tractor out far enough for the trailer to clear the curb.

What is the main cause of trailer rollover in combination vehicles?

• a.Driving too slowly
• b.Underinflated tires only
• c.Turning too fast for the load's center of gravity, especially with a high or unbalanced load✓
• d.Braking in a straight line

Most trailer rollovers happen when a driver takes a curve or ramp too fast for the load, and the high center of gravity tips the trailer. Loading cargo low and centered lowers the center of gravity and reduces rollover risk. Slowing down before curves and ramps is the best prevention.

How can you reduce the risk of rollover when loading a trailer?

• a.Load all the weight on one side
• b.Stack cargo as high as possible
• c.Leave the load loose
• d.Keep the cargo low and distribute the weight evenly to keep the center of gravity low✓

To reduce rollover risk you should keep the cargo as low as possible and spread the weight evenly across the trailer. A low, balanced load keeps the center of gravity low and improves stability in turns. High or lopsided loads make the trailer much easier to tip over.

What causes a trailer to swing out and jackknife (trailer skid)?

• a.The trailer wheels lock up and the trailer slides sideways, often from hard braking or braking in a turn✓
• b.The trailer wheels have too much traction
• c.The kingpin is greased
• d.The load is too low

A trailer jackknife happens when the trailer wheels lock and lose traction, causing the trailer to slide sideways and swing around toward the tractor. Hard braking, braking in a curve, or slippery roads can trigger it. Smooth braking and keeping traction on the trailer wheels help prevent it.

If your trailer begins to swing out in a jackknife, what should you generally do?

• a.Brake harder to stop the swing
• b.Recognize it early by watching your mirrors and release the brakes if it is a braking-induced skid to regain traction✓
• c.Turn the steering wheel sharply toward the skid
• d.Accelerate hard to straighten it

If the trailer wheels lock and the trailer starts to swing, you should recognize it early through your mirrors and, if braking caused it, ease off the brakes so the trailer wheels can regain traction and roll straight again. Continuing to brake hard keeps the wheels locked and worsens the skid. Early detection is essential because a full jackknife is hard to correct.

Why do combination vehicles need a longer following distance than smaller vehicles?

• a.Because trailers have brighter lights
• b.Because they use less fuel
• c.Because they are heavier and longer, so they take more time and distance to stop✓
• d.Because the trailer has no brakes

Combination vehicles are heavy and long, so they need much more distance and time to stop than cars. A good rule is at least one second of following distance for every 10 feet of vehicle length at low speeds, adding a second above 40 mph. More space gives you time to react and stop safely.

At 50 mph in a 60-foot combination vehicle, about how many seconds of following distance should you keep?

• a.1 second
• b.2 seconds
• c.3 seconds
• d.At least 7 seconds (6 for length plus 1 for speed over 40 mph)✓

Using the rule of 1 second per 10 feet of length, a 60-foot vehicle needs 6 seconds, and you add 1 second for speeds over 40 mph, for a total of about 7 seconds. This extra space accounts for the vehicle's long stopping distance. In bad weather or on hills you should allow even more.

Why are combination vehicles more likely to roll over than they might appear?

• a.Trucks with a high center of gravity can roll over at highway speeds on ramps even when they feel stable to the driver✓
• b.Because the trailer is always empty
• c.Because the tires are too wide
• d.Because the brakes are too strong

A loaded combination vehicle can roll over on a curve or ramp at a speed that feels safe because the driver cannot feel the trailer beginning to tip. The high center of gravity and trailer lag make rollover happen suddenly. Slowing well before ramps and curves is the safe practice.

When driving a combination vehicle on a curved highway exit ramp, what should you do?

• a.Maintain highway speed to keep momentum
• b.Slow down before the ramp to a speed well below the posted ramp limit, because the limit may be too fast for a loaded truck✓
• c.Brake hard in the middle of the curve
• d.Coast in neutral through the curve

You should slow down before entering a curved ramp, often to a speed below the posted advisory limit, because those limits are set for cars, not heavy trucks. Braking in the curve can cause a skid or rollover. Reducing speed before the curve lets you drive through it under control.

How does the trailer respond to steering inputs compared to the tractor, and why does this matter?

• a.The trailer responds instantly to steering
• b.The trailer never moves independently
• c.The trailer lags behind and can swing or off-track, so drivers must plan turns and lane changes with extra room✓
• d.The trailer steers itself

The trailer follows and reacts more slowly than the tractor, lagging behind in turns and lane changes and off-tracking to the inside. This means drivers must plan turns wide and check that the trailer clears obstacles and other lanes. Abrupt steering can make the trailer swing dangerously.

What is the safest way to brake in a combination vehicle to avoid a skid?

• a.Slam the brakes to stop quickly
• b.Pump the brakes rapidly at all times
• c.Only use the trailer hand valve to stop
• d.Brake early and smoothly, keeping the vehicle straight, so the wheels keep traction✓

You should brake early, smoothly, and while the vehicle is as straight as possible so the wheels keep traction and the trailer does not swing. Sudden or hard braking, especially in a turn, can lock the wheels and cause a jackknife. Leaving extra space lets you brake gradually.

Why should you generally avoid using the trailer hand valve (trolley/spike valve) to control the vehicle in normal driving?

• a.Applying only the trailer brakes can cause the trailer to skid and jackknife✓
• b.It turns off the headlights
• c.It raises the landing gear
• d.It disconnects the air lines

Using the trailer hand valve alone applies only the trailer brakes, which can lock the trailer wheels and cause a skid or jackknife, especially on slippery roads. Normal braking should use the foot brake, which applies brakes on all wheels together. The hand valve is not a substitute for the service brakes.

When changing lanes or merging in a combination vehicle, why must you allow extra space and time?

• a.Because the trailer has no mirrors
• b.Because the vehicle is long and the trailer off-tracks, so you need more room for the whole rig to clear✓
• c.Because the engine is slow to start
• d.Because the trailer brakes are stronger

A combination vehicle is long, accelerates slowly, and the trailer off-tracks, so you need more space and time to change lanes or merge safely. You must be sure the entire rig, including the trailing trailer, will clear other vehicles. Checking mirrors and signaling early are essential.

On a slippery road, how should you adjust your driving in a combination vehicle to prevent skids?

• a.Drive at your normal speed
• b.Brake harder than usual
• c.Reduce speed, increase following distance, and brake and steer gently to keep traction✓
• d.Use only the trailer brakes

On wet, snowy, or icy roads you should slow down, leave much more following distance, and make all inputs gentle to keep the tires from losing traction. Sudden braking or steering can cause the trailer to skid or jackknife. Smooth, gradual control is the key to staying stable on slippery surfaces.

Why is it important to check your mirrors frequently when driving a combination vehicle?

• a.To watch the sky
• b.To check the paint
• c.To read road signs behind you
• d.To monitor the trailer position, watch for trailer skids or tire problems, and confirm the trailer is tracking properly✓

Frequent mirror checks let you monitor the trailer's position, spot the early signs of a trailer skid or jackknife, and catch problems like a smoking tire or shifting load. Because the trailer lags and off-tracks, mirrors are your main way to see what it is doing. Early detection gives you time to react safely.