Vehicle knowledge: truck construction, systems, tyres and load securing
The exam tests whether you understand what keeps a heavy vehicle controllable and legal: the brake system, the driveline and exhaust after-treatment, tyre condition and load securing. You are expected to know how the systems behave when something fails and how to check them before a trip.
Brake and driveline systems
- Swiss trucks use a compressed-air dual-circuit service brake with a spring (parking) brake. If system pressure drops below the warning threshold, the spring brakes apply automatically - the vehicle fails safe, but it will stop where it is, which is why you watch the pressure gauge on descents.
- ABS prevents wheel lock; EBS adds electronic brake management and roll-stability control, which can cut engine torque if it detects an impending rollover.
- A retarder or exhaust brake is wear-free and is the correct tool for long descents: service brakes overheat, fade and can fail. Retarders act on the drive axle, so on ice or wet cobbles use them gently.
- SCR/AdBlue reduces NOx. Running the AdBlue tank dry typically triggers a power derate, not a breakdown.
Tyres
Legal minimum tread depth is 1.6 mm; for winter conditions 4 mm is the practical figure, and Swiss law requires the vehicle to be suited to the conditions rather than naming a winter-tyre rule. Check pressure cold, check twin tyres for equal pressure and similar circumference (mismatch causes heat and failure), and check load and speed indices against the axle load. Look for uneven wear indicating alignment or pressure faults.
Load securing
EN 12195-1 is the reference: secure against 0.8 g forward and 0.5 g rearward and sideways. Friction counts: about 0.6 with anti-slip mats, around 0.2 for steel on steel or wood on wood. Tie-down lashing only works if the strap angle and pre-tension are right; direct lashing is preferred for heavy single items.
Worked example
A 12 t steel load on a timber bed needs 0.8 × 12 = 9.6 t of forward securing. Without mats, friction covers 0.2 × 12 = 2.4 t, leaving 7.2 t to be held by lashings. With anti-slip mats, friction covers 0.6 × 12 = 7.2 t, leaving only 2.4 t - one well-placed direct lashing may now suffice instead of several tie-downs.
Traps
Releasing a spring brake chamber by force without chocking the wheels; riding the service brake down an alpine pass; ignoring a twin-tyre pressure mismatch; counting friction you have not actually created with mats.