This section covers your legal responsibility to keep a vehicle in a safe, roadworthy condition, including tyres, lights, mirrors, and how a load is secured, and it underpins the safety and your vehicle category on the theory test almost entirely on its own. Many of these points are also tested through the practical 'show me, tell me' questions during the driving test itself.
Learners sometimes treat this as a minor topic compared with road positioning or hazard awareness, but it's a rich source of theory test questions because the rules are precise and factual, covering exact figures like minimum tread depth that are easy to test directly.
Tyres
Tyres must have a minimum tread depth of 1.6mm across the central three-quarters of the tyre's width and around its entire circumference, and they must be free of cuts, bulges, or other damage that could cause a blowout. Checking tyre pressure regularly, including the spare, is also expected, since incorrect pressure affects both safety and fuel efficiency.
Lights, mirrors, and windscreens
All lights must work correctly and be kept clean, since a car can otherwise be invisible or misleading to other road users, particularly at night or in poor weather. Mirrors need to be properly adjusted before you set off, and windscreens must be kept clear, with any wipers or washers in working order, since an obstructed view is both a safety risk and a legal issue.
Loads and towing
A load must be secured so it can't move, fall, or create a hazard, and it must not obscure your view or stick out dangerously without appropriate markers, as covered under vehicle markings. If you're towing, you need to check the trailer or caravan is properly hitched, with working lights and, where required, a stability device, and stay within the weight limits your licence and vehicle allow.
- Minimum legal tyre tread depth is 1.6mm across the central three-quarters of the tyre.
- All exterior lights, indicators, and brake lights must work and be clean.
- Loads must be secure, balanced, and not obstruct your view or lights.
- Check mirrors and seating position before driving off, not while already moving.
Emissions and environmental checks
Vehicles must meet emissions standards appropriate to their age and type, and excessive exhaust smoke or a poorly maintained engine can result in an offence as well as an MOT failure. Keeping up with servicing isn't just about reliability, it's part of your legal responsibility as the person in charge of the vehicle.
Frequently asked questions
What is the minimum legal tyre tread depth in the UK?
1.6mm, measured across the central three-quarters of the tyre's width and around its entire circumference. Driving on tyres below this depth is an offence and a common theory test fact question.
Am I responsible for checking my vehicle even if it recently passed its MOT?
Yes, an MOT only confirms the vehicle met the required standard on the day of the test, and you're still responsible for keeping it roadworthy day to day, including tyres, lights, and fluid levels.
What should I check about a load before driving?
That it's secure and can't move or fall while driving, that it doesn't obstruct your view or lights, and that it doesn't exceed the vehicle's weight limits. Loose or overhanging loads must be properly marked if they extend beyond the vehicle.
Do all exterior lights need to be working before I drive?
Yes, headlights, indicators, brake lights, and rear lights must all function correctly, since faulty lights make your intentions and presence unclear to other road users, particularly at night or in poor visibility.
Why does the theory test include questions about emissions and servicing?
Because keeping a vehicle properly maintained is a legal responsibility, not just good practice, and poor maintenance can lead to both an MOT failure and a driving offence if it causes excessive emissions or unsafe operation.