Daily vehicle checks and heavy vehicle braking

A defect found in the yard costs a few minutes. One found by a DVSA examiner at the roadside can mean a prohibition notice, a fine and a stranded load. The LGV theory test checks both your knowledge of the walkaround check and your understanding of the braking system it protects.

The HGV walkaround check

You must check the vehicle before each journey and report defects in writing to whoever handles repairs in your organisation. DVSA’s list has more than 25 items. Rather than learn it as a list, walk it in the order you would do it.

From the cab

• View: windscreen not cracked or discoloured, nothing in the wiper sweep except permitted items such as the operator licence disc, every mirror and camera present and adjusted.
• Warning lights: including engine, emissions, ABS and EBS.
• Air build-up: pressure rises normally, the warning works, no audible leaks, and the service brake works the tractor and trailer brakes.
• Height marker: shows the real height for today’s trailer and fifth wheel setting.
• Steering, horn, seat belt, wipers and washers.

Walking round the outside

• Tyres and wheels: at least 1 mm of tread, correctly inflated, no cuts, bulges or visible cord, nothing trapped between twin wheels, and wheel nut indicators still lined up.
• Coupling: trailer correctly located in the fifth wheel, kingpin locked, secondary locking device in place, trailer parking brake working.
• Air and electrical lines: connected, clean, not chafing or kinked, nothing leaking.
• Lights, reflectors and markings: all working and clean, including side markers and conspicuity tape.
• Body: doors, curtains and landing legs secure, sideguards and rear under-run bar fitted and undamaged, spray suppression flaps present.
• Fluids: no fuel or oil leaks with the engine running, filler cap secure, enough AdBlue.
• Load: secure and not likely to move.
• Number plate clean and legible, hazard warning panels correct if you carry dangerous goods.

Electric and gas-powered lorries add checks on the high-voltage cut-off and fuel isolation switches: know where they are and that they work.

Recording it

Record the registration, date, any defects and how serious you judge them, your name and who you reported to. Record “nil defects” when you find nothing. Defects that appear during the trip are reported too; a dangerous one must be fixed before you continue.

A common wrong answer is that the check is the operator’s job alone. Both the operator and the driver are responsible.

How a heavy vehicle brakes

Lorries use air brakes. Compressed air from the engine-driven compressor is stored in reservoirs and released to apply the brakes when you press the pedal. The system has three parts:

Because the parking brake is held on by springs, a major air leak applies the brakes. Never try to move off until the pressure has built up and the low-pressure warning has gone out.

On an articulated lorry the trailer receives air through two lines. In the UK the red line is the emergency (supply) line and the yellow line is the service (control) line. Connecting them in the wrong order or forgetting the trailer park brake are both classic coupling mistakes.

Endurance brakes and long hills

An exhaust brake or retarder slows the vehicle without using the friction brakes, which is why it helps on long descents. Combined with a low gear chosen before the hill, it prevents brake fade, when overheated brakes lose effectiveness. On ice or wet roads, a retarder acting only on the drive axle can lock those wheels, so many systems are switched off or reduced in slippery conditions.

Why stopping takes longer

A loaded lorry carries far more energy than a car at the same speed, so stopping distances are longer, and a load that moves forward adds to them. An empty lorry is not automatically safer: with little weight on the axles the wheels lock more easily, and harsh braking on a bend can cause a jack-knife, where the trailer pushes the tractor round.

ABS helps keep steering control, but it does not shorten stopping distances on a poor surface. The answer the theory test wants is early, progressive braking with a long following distance.

For the official item list see DVSA’s HGV daily walkaround checks. Securing what is behind the cab is covered in load security, weights and route planning, and the LGV mock tests include braking and defect questions to check yourself against. The air tank, air line and tyre questions candidates most often look up are worked through in HGV theory test questions explained.