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BC Class 1–4 overview

BC Class 1–4: Backing and handling trailers

Backing a semi-trailer, rollovers and load height, double trailers, trailer whipping, parking a trailer and weight distribution on a tractor-trailer.

  • 12 questions
  • Topic drill
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Backing and handling trailers · Question 1Score 0/0

A parked trailer without spring brakes slowly loses its reservoir air. What happens?

Study reference: Driving Commercial Vehicles (ICBC, 2024 edition), Ch. 5 Skills for driving trucks and trailers — Backing up, Towing trailers, Swerving and whipping, Parking a trailer

All 12 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

  1. A parked trailer without spring brakes slowly loses its reservoir air. What happens?

    1. Its brakes release
    2. Nothing changes
    3. The landing gear lowers
    4. Its brakes apply harder

  2. What is trailer whipping?

    1. The trailer lifting on one side
    2. The trailer swinging side to side by itself
    3. The trailer brakes locking up on a wet road
    4. The tractor spinning its wheels

  3. How should cargo be placed to reduce rollover risk?

    1. Low, spread out and near the centre
    2. High and toward the rear
    3. On one side for balance
    4. Stacked at the front corners

  4. In a double-trailer combination, which trailer is most likely to roll over?

    1. The tractor
    2. The first trailer
    3. They are equally likely
    4. The last trailer

  5. On an evenly loaded tractor-semitrailer, about what share of cargo weight is on the steering axle?

    1. About 1 per cent
    2. About 10 per cent
    3. About 25 per cent
    4. About 45 per cent

  6. Coupling a set of doubles, which trailer goes directly behind the tractor?

    1. The lighter trailer
    2. The heavier trailer
    3. The longer of the two trailers
    4. The empty trailer

  7. Why must you never unlock the pintle hook while the converter dolly is still under the rear trailer?

    1. The air lines will freeze
    2. The dolly brakes will lock and damage the tires
    3. The tow bar can fly up and hurt someone
    4. The trailer will roll forward

  8. When backing a semi-trailer, which way do you first turn the steering wheel?

    1. The same way the trailer should go
    2. It does not matter
    3. Opposite to where the trailer should go
    4. Straight, then the same way

  9. Why turn the steering wheel back once the trailer begins to turn while backing?

    1. To stop the trailer from moving
    2. To make the trailer turn more sharply into the space
    3. So the tractor follows and avoids a jackknife
    4. To straighten the landing gear

  10. Which is a cause of trailer whipping?

    1. Slow, smooth steering
    2. A shifting load
    3. Correct tire pressure
    4. A low centre of gravity

  11. Your trailer starts to whip and then settles down. What should you do?

    1. Speed up to straighten it
    2. Brake hard with the trailer valve
    3. Keep driving, because the swerving has stopped
    4. Stop when safe and check vehicle and load

  12. When is a tractor-trailer more likely to roll over?

    1. When moving slowly in reverse
    2. When loaded and turning too quickly
    3. When parked on a slight grade
    4. When empty on a straight road

Backing and handling trailers: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Backing up a tractor-trailer (p. 77–78)

  • Backing a single-unit vehicle works like backing a car; a tractor with a semi-trailer pivots at an articulation point, which makes backing harder.
  • To start backing a semi-trailer, turn the steering wheel opposite to the direction you want the trailer to go.
  • As soon as the trailer starts to turn, turn the wheel the other way so the tractor follows the trailer's path; otherwise you risk jackknifing.
  • Backing a tractor-trailer into a normal right-angle turn traces an S-shaped path.

Off track and turns with combinations (p. 34–41)

  • A combination shows several sets of off track: the tractor's rear wheels track inside the front wheels and the trailer's rear wheels track even farther inside.
  • The farther back the fifth wheel is mounted and the longer the wheelbase or drawbar, the more off track.
  • In a right turn with a tractor-trailer, the most dangerous moment is when the tractor has turned and the trailer has not; the right mirror then shows little.
  • Turning the front wheels on too small an arc lets the trailer's rear wheels climb the curb or hit poles and cyclists.
  • In a roundabout, the trailer of a long combination may cross into the next lane; cars must yield to a combination already in the roundabout.
  • A tractor-trailer parked uphill, with or without a curb, has its wheels turned left toward the centre of the road.

Towing trailers and doubles (p. 78–79)

  • A sudden steering movement can roll a trailer, and the tractor may follow; rollovers are a major cause of death among truck drivers.
  • A loaded vehicle is more likely to roll over than an empty one; rollovers happen when turning too quickly.
  • Keep cargo low, spread out and near the centre; a higher load raises the centre of gravity and the rollover risk.
  • The higher the vehicle, the longer the trailer and the more trailers, the more important correct loading becomes.
  • With two trailers, jackknife and rollover risk rise, and the last trailer is the most likely to roll over.
  • A speed safe for a straight truck or single-trailer combination may be too fast with multiple trailers.
  • Doubles off-track more than a single trailer and may encroach on the next lane in turns.
  • Couple the more heavily loaded trailer directly to the tractor, with the lighter trailer behind.
  • Before coupling multiple trailers, apply spring brakes, or block a trailer that has no spring brakes.
  • Because backing doubles is hard, you may first disconnect the rear trailer.
  • Never unlock the pintle hook with the converter dolly still under the rear trailer; the tow bar can fly up and injure someone.
  • Deceleration lanes are often curved and may end at a stop sign or light, so slow down early with doubles.

Swerving and whipping (p. 79)

  • Whipping or swerving is a trailer moving back and forth across the road independently of the tractor.
  • Causes: speed too high for conditions, sudden steering, improper trailer connections, shifting loads, dragging brakes, a flat tire.
  • If a trailer whips, slow down and stop as soon as it is safe, then check the vehicle and load even if the swerving stopped.

Parking a trailer (p. 80)

  • Block the wheels of a parked trailer.
  • Trailer reservoir air bleeds down over time; without spring brakes the trailer brakes then release, with spring brakes they stay applied.
  • Spring brakes stay effective only if the brakes are properly adjusted.

Jackknife and combination braking (p. 25–26)

  • Applying only the trailer brakes, or braking too hard on slippery roads, can lock wheels and jackknife a combination.
  • A full jackknife is tractor and trailer at 90 degrees or less to each other; it can happen at very low speeds.
  • Misuse of retarders on slippery roads can lock the drive wheels and jackknife a tractor-trailer.
  • If any unit in the combination lacks ABS, brake as if none had ABS.

Loading combinations (p. 93–94)

  • A heavy load sitting over the trailer's rear tires leaves the fifth wheel unsupported; the tractor's drive tires slip and braking is uneven.
  • An average semi-trailer's central weight point is about the middle of the trailer.
  • Evenly loaded trailers carry about 45 per cent of cargo weight on the trailer axles, 45 per cent on the drive axles and 10 per cent on the steering axle.
  • A tridem drive truck or tractor must carry, loaded, at least 25 per cent of the tridem axle weight on its steering axle, or 40 per cent with twin steering axles.

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