Vehicle technology, inspection and maintenance of bus and trailer
This domain tests the technical checks a professional driver owns: the coupling, the trailer brake system, tyres, lights and the inspection regime. Questions often present a defect and ask whether the combination may be driven - usually the answer is no.
What is checked and how often
Buses and trailers with a permitted total weight above 3.5 t go to periodic inspection (syn) every year at an approved inspection hall, with the first inspection scheduled from the registration date. Inspection covers brakes on rollers, lights, steering, suspension, tyres, chassis corrosion, the coupling, and the trailer's breakaway brake and cable.
The coupling
Bus trailers are normally coupled with a drawbar eye or a heavy ball coupling rated by its D-value, with a lock indicator, a safety cable or breakaway system, and a 13-pin electrical connector. Before every trip: lock engaged and secured, cable attached to a rated point (never looped over the ball), plug seated, and lights checked on both vehicles - indicators, brake, tail, fog and reverse.
Brakes and air systems
- The trailer's service brake is actuated from the bus and must apply automatically if the coupling separates.
- Check that air pressure builds and holds, drain the tanks, listen for leaks, and test the parking brake on a slope.
- ABS/EBS warning lamps must go out after the self-test; if they stay on, the vehicle is not fit for service.
Tyres and structure
Check tread depth against the legal minimum for the class and the wear indicators, sidewall damage, and matching sizes across an axle. Check the trailer floor for rot, the doors and locks, mudguards and marker boards.
Daily walk-around
Lights, tyres, coupling, breakaway, load, fire extinguisher, first-aid kit, warning triangle, hi-vis vests and tachograph. Any defect affecting safety must be reported and the vehicle taken out of service.
Worked example
The trailer's ABS lamp stays lit after the self-test and a brake test shows the trailer wheels locking early. An ABS fault on a vehicle required to have ABS is a defect that puts the combination off the road. The correct action is to report it and not to drive, because the trailer will lock and swing out under heavy braking - and the annual inspection would fail it anyway.
Traps
- Checking only the bus lights and not the trailer's.
- Looping the safety cable over the tow ball.
- Treating a warning lamp as a nuisance rather than a defect.
- Forgetting that the trailer carries its own inspection date.