DVSA says nearly 50% of MOT faults could be avoided by simple maintenance. Lighting and signalling caused 30% of faults and tyres 10%. Checking bulbs, tyre tread (1.6mm minimum), wipers, washer fluid and brake fluid before the test removes the most common causes.
Checked 23 October 2026 against the DVSA MOT inspection manual
- Avoidable faults: Nearly 50% (DVSA)
- Lighting share of faults: 30%
- Tyre share of faults: 10%
- Car tread minimum: 1.6mm
Why simple checks matter
DVSA has said that nearly 50% of all faults found at MOTs could be avoided by regular, simple maintenance. That figure places routine checks at the centre of any effort to reduce common fails. The faults concerned are not obscure defects requiring specialist equipment. They arise from items that deteriorate gradually and can be spotted before a test. Understanding this proportion helps explain why a short inspection before an MOT can make a meaningful difference to the outcome.
In DVSA's 2014 to 2015 data, lighting and signalling made up 30% of all faults and tyres 10%. Together these two categories account for a substantial share of defects recorded at test. Both are areas where simple checks are possible without tools or technical training. A failed lamp or a tyre below the legal tread depth is straightforward to identify. The scale of these figures shows how often such defects appear across the testing system.
These figures are from DVSA's 2014 to 2015 data and illustrate where avoidable faults concentrate. The value of simple checks lies in catching deterioration early, before it becomes a recorded fail.
Lights and tyres
The DVSA lights check covers every lamp on the vehicle, including headlights, indicators, brake lights and number plate lamps. The agency advises tapping bulbs to check they are not loose or damaged, and checking the light colours are correct.
Tyre condition is assessed alongside lights in the DVSA checks. The agency advises checking tyre tread depth, with 1.6mm the minimum for cars. Tyre pressures should also be checked, tyres should be the same size, and the sidewalls inspected for cuts or bulges.
These checks are quick to carry out before an MOT test.6mm tread can each produce a common fail. Checking pressures, matching tyre sizes and looking for cuts or bulges on every tyre helps avoid problems being recorded on the day.
Brakes and view of the road
Brake performance is a core part of the MOT, so the DVSA advises listening for unusual brake noises during normal driving. It also recommends noticing whether the car pulls to one side when the brakes are applied. Under the bonnet, the brake fluid reservoir should be checked and the level confirmed as sitting between the high and low marks.
Wipers and washers must work properly for the MOT. The DVSA advises replacing damaged blades, and also blades that are over a year old. Washer fluid should be topped up so the system can be checked. Stickers and hanging items should be kept off the windscreen, as these can obstruct the driver's view.
The view of the road matters as much as the equipment itself. A windscreen with large chips should be replaced. Mirrors should be checked too, confirming they are present, secure and give a clear view. Together with working wipers and washers, these checks support the clear forward and rear vision the test requires.
Other items checked on the day
The MOT checks that the horn works, that registration plates are secure and correctly formed and spaced, that seatbelts are present and working, and that seats are secure. These items are inspected alongside the rest of the vehicle on the day. A horn that fails to sound, a plate that is loose or wrongly spaced, or a seatbelt that does not operate will be recorded as a defect. Seats that are not secure are also noted. Checking these before arrival helps avoid common fails.
Warning lights are checked, including the airbag, ABS or ESC, and electronic power steering lights. On cars first used on or after 1 January 2012, the tyre pressure monitoring light is also checked. A light that stays on or fails to illuminate as expected is recorded. These checks form part of the inspection and are separate from the items covered elsewhere in this guide.
The fuel cap must be opened during the test, so the key should be brought. Diesel cars should arrive with a fully warmed-up engine. These two points are easy to overlook but affect how the inspection proceeds on the day. Bringing the key and ensuring the engine is warm allow the relevant checks to be carried out without delay.
Frequently asked questions
How many MOT faults could be avoided with simple maintenance?
The DVSA said nearly 50% of all faults found at MOTs could be avoided by regular, simple maintenance. That makes a basic pre test check worthwhile before the test date.
Which areas cause the most MOT failures?
In DVSA data for 2014 to 2015, lighting and signalling made up 30% of all faults and tyres 10%. These two areas alone account for a large share of common failures.
What does the DVSA advise for checking lights before an MOT?
The DVSA advises tapping bulbs to check they are not loose or damaged and checking the light colours are correct.
What tyre checks does the DVSA recommend before the test?
The DVSA advises checking tyre tread depth, with 1.6mm the minimum for cars, tyre pressures, that tyres are the same size, and looking for cuts or bulges. Worn or damaged tyres are a common cause of failure.
What should be brought and prepared for the MOT test itself?
The fuel cap must be opened, so the key should be brought. Diesel cars should arrive with a fully warmed up engine. The MOT also checks the horn, registration plates, seatbelts and seats.
Part of the MOT guide series
MOT check: the full guide › What the MOT checks
How Long Does an MOT Take? Typical Times and What Affects Them ›
