What is the legal minimum tyre tread depth for cars?

At least 1.6 mm across the central three-quarters of the breadth of the tread and around the entire circumference. The same minimum applies to light vans and light trailers. Motorcycles, large vehicles and passenger-carrying vehicles need at least 1 mm, and mopeds should have visible tread.

When should you check your tyre pressures?

Weekly, before a journey, while the tyres are cold. Warm or hot tyres can give a misleading reading. Inflate them to the vehicle manufacturer's specification for the load you are carrying, as shown in the handbook, because incorrect pressures affect braking and steering.

What does it mean if a warning light stays on after the engine starts?

Most dashboard warning lights come on with the ignition and go out once the engine starts, apart from the handbrake light. If one stays on, or comes on while you are driving, stop and investigate, because Annex 6 of The Highway Code says it could indicate a serious fault.

Does ABS mean you will stop in a shorter distance?

No. Anti-lock brakes should help you keep steering control during heavy braking, but rule 120 of The Highway Code warns not to assume a vehicle with ABS will stop in a shorter distance. In an emergency, brake firmly and keep the pressure on.

How often should you check your car's fluid levels?

At least weekly, according to Annex 6 of The Highway Code. Low brake fluid may result in brake failure and a crash, so learn what the low fluid warning lights look like. Before winter, make sure the radiator and windscreen bottle contain suitable anti-freeze.

Safety & Your Vehicle: Tyres, Lights & Seat Belts

What is the legal minimum tyre tread depth for a car?

Cars, light vans and light trailers must have at least 1.6 mm of tread across the central three-quarters of the breadth of the tread and around the entire circumference, according to Annex 6 of The Highway Code. Larger vehicles and motorcycles have a lower minimum, and all tyres should be free from cuts and other defects.

Vehicle	Legal minimum tread	Where it applies
Cars, light vans, light trailers	1.6 mm	Central three-quarters of the breadth, around the entire circumference
Motorcycles, large vehicles, passenger-carrying vehicles	1 mm	Three-quarters of the breadth, in a continuous band around the entire circumference
Mopeds	Visible tread	Whole tyre

If a tyre bursts while you are driving, grip the steering wheel firmly and let the vehicle roll to a stop at the side of the road. Annex 6 also warns that some vehicle defects can attract penalty points.

When and how should you check tyre pressures?

Check tyre pressures weekly, before your journey, while the tyres are cold, because warm or hot tyres can give a misleading reading. Use the figures in your vehicle handbook and inflate to the manufacturer’s specification for the load you are carrying. Under-inflated or over-inflated tyres adversely affect both your braking and your steering.

Excessive or uneven tyre wear can point to faults in the braking or suspension systems, or wheels out of alignment, and Annex 6 says to have these corrected as soon as possible. A car that pulls to one side when braking most likely has a brake fault or incorrectly inflated tyres.

What should you do if a warning light comes on?

Stop and investigate. When you turn the ignition, warning lights come on and should go out once the engine starts, except the handbrake warning light. If one stays lit, or comes on while you are driving, Annex 6 of The Highway Code says you could have a serious fault. Learn every symbol from your handbook.

Charge warning light: the battery may not be charging. Get it checked as soon as possible to avoid losing power to the lights and other electrical systems.
Brake fluid: low brake fluid may result in brake failure. Check fluid levels at least weekly.
Overheating: wait until the engine has cooled naturally before removing the coolant filler cap.
Fire: get everyone out to a safe place and call the fire brigade. Do not open the bonnet, as that makes the fire flare.

How do anti-lock brakes (ABS) help in an emergency?

ABS is designed to stop the wheels locking under heavy braking so that you keep steering control. In an emergency, apply the footbrake firmly and do not release the pressure until the vehicle has slowed to the speed you want (rule 120). But ABS does not guarantee a shorter stop, so never follow more closely because of it.

Without ABS, rule 118 says brake immediately but try to avoid braking so harshly that you lock the wheels, because locked wheels can lead to loss of control. In normal driving, rule 117 says brake early and lightly, then more firmly as you begin to stop.

What other vehicle faults does the theory test ask about?

Expect questions linking a symptom to its likely cause. Heavy steering often means an under-inflated or punctured tyre. A car that keeps bouncing after you push down on the front or rear has worn shock absorbers. Unusual smells, such as burning rubber, petrol or an electrical fault, need investigating immediately to avoid the risk of fire.

Vibration through the steering wheel at certain speeds is commonly caused by wheels that need balancing, so have a garage check it.
Lights, indicators, reflectors and number plates must be kept clean and clear, and windscreens and windows free from obstructions.
Spilt diesel makes the road very slippery, especially for motorcyclists. Do not overfill your tank, and make sure the fuel cap is fastened securely.
Never smoke or use a mobile phone on a petrol station forecourt.

How can you cut fuel use and emissions?

Switch off rather than idle. You must not leave a parked vehicle unattended with the engine running, or leave the engine running unnecessarily while stationary on a public road (rule 123). If you are likely to be stationary for more than a couple of minutes, apply the parking brake and switch off the engine.

Leaving the engine running is permitted when you are stationary in traffic or diagnosing faults. Annex 6 says exhaust emissions must not exceed prescribed levels, and a catalytic converter helps by reducing harmful gases in the exhaust. Correct tyre pressures, smooth acceleration, planning ahead and removing roof racks or boxes you are not using all help to save fuel.

How do you keep your car secure?

When you leave your car, remove the key and engage the steering lock, lock it even if you are only away for a few minutes, close the windows completely, and take valuables with you or lock them in the boot. Never leave vehicle documents in the car, or children and pets in an unventilated car.

Annex 6 suggests fitting an anti-theft device such as an alarm or immobiliser, and having your registration number etched on all your windows as a cheap deterrent to professional thieves.

What mistakes do learners make on safety and your vehicle questions?

Most errors come from half-remembered figures and from treating a warning sign as something to monitor rather than act on. These traps catch learners most often. When two options look similar, pick the one that matches the exact wording of the Highway Code, especially on tread depth and ABS.

Tread depth across the whole tyre. The 1.6 mm minimum applies across the central three-quarters, around the full circumference.
Checking pressures after a long drive. Check them cold.
Believing ABS shortens stopping distances. Rule 120 says do not assume it will.
Pumping the brake with ABS. Keep firm, steady pressure on the pedal.
Opening the bonnet on an engine fire. It makes the fire flare.
Idling to warm the engine. Rule 123 says do not run the engine unnecessarily while stationary.

Where should you go next?

Vehicle safety questions are easy marks once the key figures stick, so test yourself now while they are fresh. Use the links below to practise this topic, then move on to the topics that build on it, such as safety margins and handling in bad weather.