Safe Driving Practices for Heavy Vehicles
What this domain tests
This domain tests whether you can turn physics into habits: speed selection, following distance, brake management on grades, and the space a heavy combination needs to turn and stop.
The core ideas
- Kinetic energy rises with the square of speed. Doubling speed quadruples braking energy; a loaded tractor-trailer at 100 km/h needs well over 150 m to stop on dry pavement, and far more when wet.
- Following distance: at least 4 seconds behind the vehicle ahead at highway speed when loaded, more on wet or icy roads or with a heavy load. Count by picking a roadside object and saying "one-thousand-and-one" until you reach it.
- Grades: select the gear before the descent, not on it. Use the engine brake or retarder as primary control, then brake firmly for a few seconds (snubbing) to bring speed down and release. Riding the brakes heats them and causes fade.
- A runaway lane is a decision you make early, not a last resort.
- Off-tracking: the trailer cuts inside the tractor's path. On a right turn, take the turn wide, watch the right mirror through the whole turn, and check for cyclists on your right.
- Blind spots: directly in front, both sides along the trailer, and several vehicle lengths behind. If you cannot see the other driver's mirrors, they cannot see you.
Worked example
You descend a 6% grade posted at 60 km/h for trucks with a 30,000 kg load. Before the crest you shift down and set the retarder. Speed creeps to 68 km/h; you brake firmly to 55, release, and let the engine hold it. If speed keeps climbing after two snubs, the grade is steeper than your gear choice - take the runaway lane rather than ride the brakes to failure.
Traps that cost marks
Assuming ABS shortens stopping distance on ice (it allows steering, it does not shorten the stop); treating the posted limit as a target speed on a curve with a high centre of gravity; and forgetting that an empty trailer bounces and brakes differently from a loaded one.