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Vehicle Maintenance, Safety and Security

The UK Highway Code provides information and rules about vehicle maintenance, safety and security. It includes some general guidance for drivers besides that which they must obey.

Rules on Vehicle Maintenance and Safety

Certain devices need more upkeep than others. Drivers and riders should take special care to make sure all these are in good working order:

  • Brakes and lights
  • Exhaust system
  • Seat belts
  • Steering
  • Windscreen wipers, washers, and demisters

Besides this, the UK Highway Code wording clarifies the law further by using the words MUST and MUST NOT.

  • Lights, indicators, reflectors, and number plates MUST be kept clean and clear.
  • Windscreens and windows MUST be kept clean and free from obstructions to vision.
  • Lights MUST be properly adjusted to prevent dazzling other road users. Pay extra attention this one if you are driving a heavily loaded vehicle.
  • Exhaust emissions MUST NOT exceed prescribed levels.
  • Make sure any items of luggage are securely stowed.
  • Ensure the seat, seat belt, head restraint, and mirrors are correctly adjusted before setting off on a journey.

Vehicle Warning Displays

You should understand the meaning of all warnings that display on the vehicle instrument panel. Do not ignore these vehicle warning signs. As a rule, they indicate the development of a dangerous fault.

  • Dashboard lights illuminate when you turn the ignition key. They should go out when the engine starts (except for the handbrake warning light). It could indicate a serious fault if they do not go out, or if they light up while driving. In this case, stop the vehicle in a safe place and investigate the problem.
  • It usually means the battery is not charging if the charge warning light comes on while driving. Check this without delay to avoid a loss of power to the lights and to other electrical systems.

Window Tints

You MUST NOT use a vehicle with excessively dark tinting applied to the windscreen, or to the glass in any front window to either side of the driver. Any window tinting applied during the manufacture will comply with the Visual Light Transmittance (VLT) standards.

Note: The rules on legal window tint provide further details. VLT limits do not apply to rear passenger windows or a rear windscreen.


Tyres MUST be correctly inflated to the vehicle manufacturer’s specification for the load being carried. Always refer to the vehicle handbook or data. Tyres should also be free from certain cuts and other defects.

Cars, light vans and light trailers MUST have a tread depth of at least 1.6 mm across the central three-quarters of the breadth of the tread and around the entire circumference.

Motorcycles, large vehicles and passenger-carrying vehicles MUST have a tread depth of at least 1 mm across three-quarters of the breadth of the tread and in a continuous band around the entire circumference.

Note: Mopeds should have visible tread. Some vehicle defects can result in driving licence penalty points.

Tyre Pressures

The UK Highway Code laws and guidance recommend you check vehicle tyre pressures on a weekly basis. Check the pressure while the tyres are cold (e.g. before a journey). You may get a misleading pressure reading when the tyres are warm or hot.

Under-inflated or over-inflated tyres can adversely affect the braking and steering systems. Faults in the braking or suspension systems, or wheels out of alignment, may cause excessive or uneven tyre wear. You should correct these kinds of vehicle faults as soon as possible.

Tyre Punctures and Flats

Try to keep control of the vehicle if a tyre bursts while driving or riding. Keep a firm grip on the steering wheel and let the vehicle roll to a complete stop at the side of the road.

Stop the vehicle as soon as it is safe to do so if you have a flat tyre. Only change tyres if you can do so without putting yourself or others at risk. If not, call a vehicle breakdown service.

Fluid Levels

Check the vehicle fluid levels on a regular basis (at least once a week). Low brake fluid may result in brake failure – which can lead to a crash. Make sure you know how to recognise low fluid warning lights in vehicles that have them fitted.

Checks Before Wintertime

Be familiar with the procedures for driving in adverse weather conditions before winter arrives. Always keep the battery well maintained and make sure there are appropriate antifreeze agents in the radiator and windscreen bottle.

Other General Problems with Vehicles

There are several checks you can make yourself to prevent a worsening of some general and common problems. So if the vehicle:

  • Pulls to one side when braking: It is likely to be incorrectly inflated tyres or a brake fault. If so, consult a garage or mechanic without delay.
  • Continues bouncing after pushing down on the front or rear: Usually means the shock absorbers are worn. Driving with worn shock absorbers seriously affects the operation of a vehicle. Replace them as soon as possible.
  • Smells of anything unusual (e.g. burning rubber, an electrical fault, or petrol): Investigate a problem such as this immediately to avoid risking a vehicle fire.

Overheated Engine (or vehicle fire)

In fact, most modern car engines are water-cooled. If the engine overheats you should allow it time to cool down ‘naturally’. Make sure it has cooled before removing the coolant filler cap and adding water or other coolant.

Get the occupants out of the vehicle quickly and to a safe place if it catches fire. Do not attempt to extinguish a fire in the vehicle engine compartment. Opening the bonnet will make the fire flare. Instead, stay in a safe area and call the fire brigade.

At a Petrol Station (fuel tank and fuel leaks)

Avoid spilling fuel on the forecourt when filling up the vehicle tank or any fuel cans you are carrying. Report any spilled fuel immediately to the petrol station attendant.

Diesel spillage is dangerous to other road users, particularly motorcyclists. It will ‘significantly’ reduce the level of grip between tyres and the road surface. So, double-check for fuel leaks and make sure:

  • You do not overfill the fuel tank.
  • The seal in the cap is not torn, perished, or missing and it is securely fastened.
  • There is no visual damage to the cap or to the fuel tank. Any emergency fuel caps fitted should form a good seal.

Note: Never smoke, or use a mobile phone, on the forecourt of petrol stations. These are major fire risks and could cause an explosion.

Information about Vehicle Security

To help keep it safe and secure, any time you leave the vehicle unattended you should:

  • Remove the ignition key and engage the steering lock.
  • Lock the car or motorbike (even if you only leaving it for a few minutes).
  • Take all contents with you, or lock them in the boot compartment. A carrier bag looks like it might contain valuables to a thief!
  • Close all the windows completely.
  • Never leave children or pets in an unventilated car.
  • Never leave vehicle documents in the car.

You can fit an anti-theft device for extra security (e.g. an alarm or an immobiliser). It is wise to check the level of built-in security features if you are buying a new car or motorbike.

Consider having the vehicle registration number etched on all the car windows. It is an inexpensive and effective deterrent to professional vehicle thieves.

Vehicle Maintenance, Safety and Security: The Highway Code in the United Kingdom