Over-braking with a trailer can sometimes lead to
- turbulence.
- slowing down.
- jackknifing. ✓
- none of the above.
Answer: C. jackknifing.
Over-braking with a trailer can lead to jackknifing, where the tractor and trailer fold toward each other.
Why this is the answer
The handbook describes a full jackknife as the tractor and trailer forming an angle of 90 degrees or less to each other, and notes it can happen even at very low speeds. It says jackknifing is often caused by poor braking techniques, including improper use of retarders. Braking badly or too hard with a trailer is exactly that kind of poor technique, so the folding of the unit is the result the handbook ties to it. Practising with ABS is suggested so you know how it feels.
Why the other answers are wrong
- A. turbulence. — Turbulence is moving air, and nothing in the braking passages connects it to trailer braking.
- B. slowing down. — Slowing down is just what braking is meant to do, not a hazard that results from over-braking.
- D. none of the above. — The handbook does name a real result of poor braking technique with a trailer, so saying none of these apply is wrong.
Remember it
Smooth brake pressure keeps the tractor and trailer in line; grabby braking lets the unit fold.
Official handbook: ICBC Driving Commercial Vehicles, 2 Heavy vehicle braking – Braking, p. 26