Bus Vehicle Technology and Vehicle Checks
Domain 3 covers bus technology and the daily vehicle check: what the systems do, what you must inspect before departure, and which defects mean the vehicle stays parked.
Technology
- Buses are M2 (up to 5 t) or M3 (over 5 t) vehicles. Most category D buses use dual-circuit compressed-air service brakes with spring-loaded parking brakes that apply automatically when air pressure drops.
- A retarder or engine brake saves the service brakes on long descents; use it gently on slippery surfaces, because it acts on the driven wheels only.
- Pneumatic doors have an interlock so the bus cannot be driven with a passenger door open. Each door also has an emergency release; emergency hammers, roof hatches and marked exits complete the escape routes.
- ABS, ESC, the 100 km/h speed limiter, tachograph, kneeling or ramp for wheelchair access, seat belts where fitted, fire extinguisher, first-aid kit, warning triangle and vest are part of the equipment.
Daily walk-around check
- Lights, indicators, brake lights, mirrors, wipers, washer, horn.
- Tyres: pressure, cuts, bulges, tread depth; wheel-nut indicators aligned.
- Body, glazing, doors, steps, handrails, ramp, belts.
- Fluids: oil, coolant, AdBlue, washer; no leaks under the vehicle.
- Safety equipment: extinguisher seal and pressure, complete first-aid kit, hammers present, hatches closing properly.
- Air brake test: build up pressure, check the low-pressure warning, listen for leaks, confirm the parking brake holds on a slope.
- Tachograph: correct time, driver card inserted, no fault messages.
Worked example
The low-pressure warning sounds two minutes after starting and pressure stays at 5 bar. The bus must not be dispatched: the compressor, governor or a leaking circuit is faulty, and as pressure falls the spring brakes will apply - possibly while driving. The dispatcher is informed and a replacement vehicle ordered.
Traps that cost marks
- Relying on the door interlock instead of physically checking doors and emergency releases.
- Driving with an ABS or ESC warning light on.
- Opening the engine cover fully during a fire check.
- Ignoring a tachograph fault message.
- Skipping the brake test because the bus was fine yesterday.