When did you last check your tyres, wipers, or even your number plates? Are you sure your car is legally safe to drive on UK roads today?
In the UK, vehicle safety and roadworthiness are more than just recommendations they’re legal requirements. Every driver is obligated by law to ensure that specific components of their vehicle are in good working condition at all times. Failing to do so can lead to serious consequences, including fines, points on your driving licence, an MOT failure, or even prosecution in severe cases.
While many motorists rely on the annual MOT test to assess their vehicle’s condition, it’s essential to understand that maintaining a roadworthy vehicle is a daily legal responsibility. Certain parts must always meet legal standards, and neglecting them—even outside of MOT periods, can leave you liable.
In this guide, we’ll explore which car parts the law specifically requires you to maintain, why these regulations exist, and what can happen if you don’t follow them.
What Are the UK Laws on Vehicle Roadworthiness?
In the United Kingdom, the legal foundation for vehicle roadworthiness is primarily set by the Road Traffic Act 1988 and the Road Vehicles (Construction and Use) Regulations 1986. These laws state that it is illegal to use a motor vehicle on a public road unless it is in a condition that does not pose a risk to its occupants or other road users.
The Driver and Vehicle Standards Agency (DVSA) oversees compliance, supported by MOT testing requirements and spot checks by police or enforcement officers. While passing an MOT test proves that your vehicle met the required standards on that day, it does not guarantee roadworthiness for the remainder of the year. Drivers are still responsible for making sure their vehicles remain safe and legal.
If your car is found to be unroadworthy, even with a valid MOT certificate, you may still be fined or face prosecution. The law makes it clear: a roadworthy vehicle is a legal necessity not a convenience.
What Car Components Must Be Kept in Good Condition by Law?
The law identifies several key components of a vehicle that must be kept in consistently safe and working order. These include items that affect the vehicle’s visibility, control, emissions, and safety in the event of a collision. Neglecting these can compromise not only your legal standing but also the safety of yourself and others on the road.
1. Lights
Yes, the law mandates that all exterior lights must be operational, clean, and properly aligned. This includes your vehicle’s front and rear lights, brake lights, indicators, fog lamps, reverse lights, and the number plate illumination.
These lights are critical for visibility, both for the driver and for other road users. Lights that are dim, broken, or misaligned can make it harder for you to see and for others to spot your vehicle, especially in poor weather or during nighttime driving.
Improperly functioning lights can result in a failed MOT test or a roadside fine. For instance, if you’re caught driving with a faulty brake light or headlamp, you may face a £100 fixed penalty notice, and repeat offences could attract points on your licence.
2. Windscreens and Wipers
Absolutely. Your windscreen is a vital part of your visibility system, and its condition is legally regulated. If your windscreen is chipped, cracked, or otherwise damaged in a way that obstructs your view, it can make the vehicle unsafe to drive and could be classified as unroadworthy.
The wipers must be capable of cleaning the windscreen effectively. Worn-out blades, streaking, or failure to clear rainwater or debris can lead to visibility issues and legal penalties. In addition, it is a legal requirement to ensure that your washer fluid is topped up. Driving without washer fluid is surprisingly a fineable offence under UK law.
3. Mirrors
Yes, under UK vehicle regulations, your car must be equipped with at least two functioning mirrors, typically the interior rear-view mirror and the driver-side external mirror. If the interior mirror is blocked (for example, by a load), both external mirrors must be operational.
These mirrors are crucial for safe driving, enabling you to monitor traffic behind and to the sides. Missing or broken mirrors impair your ability to make safe lane changes, overtake, or reverse.
A car with a damaged or missing mirror is considered unsafe and could be stopped by police or fail its MOT. Repair or replacement should be done immediately to avoid any breach of the law.
4. Seat Belts
Yes. Seat belts are one of the most important safety features in any vehicle, and the law is very clear about their maintenance and use. All seat belts must function correctly, meaning they should fasten securely, retract properly, and show no signs of fraying, cuts, or damage.
The law also applies to rear seat belts and requires them to be used by passengers when the vehicle is in motion. If seat belts are missing or defective, the vehicle will fail its MOT, and the driver could be penalised for endangering passengers.
In newer vehicles, seat belt warning systems (usually dashboard lights and alerts) must also be operational as part of the vehicle’s safety system.
5. Tyres
Tyres are one of the most strictly regulated vehicle components due to their direct impact on road grip, braking distances, and handling. UK law requires all tyres to have:
- A minimum tread depth of 1.6mm across the central 75% of the tyre
- No cuts, bulges, or exposed cords
- Appropriate tyre pressure according to manufacturer recommendations
- Matching sizes and types suitable for the vehicle
Failure to comply with tyre laws can lead to significant penalties. Each illegal tyre can incur a fine of up to £2,500 and three penalty points, meaning all four tyres in poor condition could cost a driver £10,000 and 12 points, enough for an instant disqualification.
6. Emissions and Exhaust Systems
Yes. A vehicle’s exhaust system must function correctly and not emit excessive smoke or noise. Emissions are tested during MOTs to ensure they fall within legal environmental standards. Cars must be equipped with appropriate emissions control devices, such as catalytic converters or diesel particulate filters (DPFs).
If a vehicle’s exhaust is leaking or if visible smoke is coming from the tailpipe, the car may be deemed unroadworthy. Emissions that exceed legal limits could result in MOT failure and fines if the issue is not resolved promptly.
7. Number Plates
Yes, number plates must follow strict formatting and visibility laws. They must be:
- Clearly visible and clean
- Made from reflective material
- Displayed in the correct font and spacing
- Free of cracks, fading, or covers that obscure visibility
Driving with a number plate that cannot be easily read, due to dirt, damage, or illegal formatting, can result in a fine of up to £1,000 and may also affect your vehicle’s MOT outcome.
8. Steering and Suspension Components
Yes. The vehicle’s steering system must operate smoothly and accurately. Excessive play or stiffness could indicate underlying mechanical issues, which are both a safety hazard and an MOT failure point.
Similarly, the suspension system, including shock absorbers, springs, and linkage,s must be free from wear or damage. A worn-out suspension can compromise the vehicle’s handling, especially during braking or on uneven roads.
Steering and suspension faults can be difficult to detect early, so regular servicing and test drives by a qualified mechanic are essential for ongoing compliance.
What Are the Legal Requirements for Key Car Components?
| Component | Legal Requirement | Risk of Non-Compliance |
| Tyres | 1.6mm tread depth, correct type and pressure | £2,500 fine + 3 points per tyre |
| Lights | All must work, properly aligned and clean | MOT failure, £100 fine |
| Windscreen/Wipers | No major cracks; wipers must clear effectively | MOT failure, roadside fine |
| Mirrors | At least two functional mirrors required | MOT failure, fine |
| Seat Belts | Fully working and damage-free for all seats | MOT failure, driver penalty |
| Exhaust & Emissions | No leaks; emissions within legal limits | MOT failure, environmental fines |
| Number Plates | Legible, reflective, correctly formatted | £1,000 fine, MOT failure |
| Steering & Suspension | No excessive play, wear or failure in handling | MOT failure, safety risk |
What Can Happen If You Drive an Unroadworthy Vehicle?
The legal consequences of driving an unroadworthy vehicle are severe. If caught, you may face:
- Fixed penalty notices or court summons
- Fines up to £2,500 per defect
- Penalty points (3 per offence for tyres and other major faults)
- Vehicle seizure for dangerous defects
- Invalidated insurance in case of an accident
- Immediate driving ban for multiple offences
Beyond the legal issues, driving a car in poor condition puts everyone at risk. Brake failure, bald tyres, or poor visibility can lead to accidents, injury, or even death.
FAQs
What should I check monthly to ensure my car is legal?
Tyres, lights, wipers, mirrors, washer fluid, and number plate visibility should be checked regularly. Also, look out for unusual noises in the brakes or steering.
Can a car pass its MOT but still be unroadworthy?
Yes. An MOT only confirms roadworthiness at the time of the test. Any deterioration after that can still make your car illegal to drive.
Are dirty number plates really illegal?
Yes. If your number plate cannot be read due to dirt, it is considered non-compliant and you may receive a fine.
Is washer fluid legally required in the UK?
Yes. You must ensure your windscreen washers are functional and contain fluid. Running out can result in MOT failure or a fine.
What happens if my seat belts are worn out?
Frayed or malfunctioning seat belts will fail an MOT and may make your vehicle unroadworthy. They must be repaired or replaced immediately.
Can I be fined for having a cracked windscreen?
Yes. Cracks that obstruct your view are illegal and will cause an MOT failure. Police can also issue fines during checks.
How do I know if my steering system is failing?
Signs include stiffness, excessive play, unusual noises when turning, or drifting while driving. If any of these occur, have the car inspected immediately.
