The CO Research Trust has responded to the Department of Transport's (DfT) “Changes to the date of the first MOT test and research into other MOT enhancements” consultation.

The DfT is seeking views on whether the timeframe for the first date a vehicle should be MOT tested (currently 3 years) should be changed. They are also looking for evidence and views on other suggested changes to MOT testing that may enhance safety.

The Trust has taken this opportunity to brief the DfT on its recently funded project, carried out by Dr Sophie Duggan of AirSafe London.

The Trust's Response

In response to these critical questions being raised, the Trust has submitted the below response.

To summarise, the Trust considers that the MOT test could be moved from three years to four years, for the first test.

This would reduce operating costs for drivers and may, be an appropriate adjustment given improved car safety design.

However, in order to safeguard public health, increasing the testing schedule regarding emissions would be appropriate. For the same reasons, the Trust recommends testing on MOT for the presence of in-cabin leakage of exhaust gas.

The shift to electric vehicles from internal combustion engine vehicles is likely to be accompanied by the disparity in ownership across income groups, with resulting health inequality. The MOT test will need to prioritise and address key features of this inequality. The Trust strongly suggest that in-cabin air quality is one such feature.

The AirSafe project

Recent studies have shown that the air inside cars can contain dangerous levels of carbon monoxide (CO). Carbon monoxide (CO) levels within the passenger cabins of cars approach, and in some cases exceed, WHO limits.

Driving on heavily-polluted roads exposes passengers to raised levels of CO through the air intake of the car. However, in-car CO exposure depends not just on the quality of air outside the car, but on the performance of systems within the car as well.

A comparison of in-car CO values and ambient CO indicates that this is likely to be due to internal leakage of exhaust gases, rather than to simple ingress of external pollution. To date, however, no comparable study has been published within the UK.

AirSafe London began investigating this issue in 2018, supported by the CO Research Trust and have carried out two phases of testing to date. Of 26 cars tested, nine showed significantly elevated in-car CO levels.

AirSafe London

The public health implications of this are significant, particularly for people who spend a considerable amount of time driving.

The goal of AirSafe London is to help protect passengers and to achieve this, they need to test more vehicles, to obtain good-quality data.

Below is a lecture given by Dr Sophie Duggan on the results of the AirSafe project.


The MOT test has been in place since the 1960s and the 3-year threshold for the first MOT test since the late 1960s.

The MOT logo

The MOT test was first introduced to assure the safety of a vehicle, in practice the effectiveness of safety-critical components such as tyres and brakes. In recent years, the concept of roadworthiness has expanded to encompass vehicle emissions and their effects on the environment.

Emissions test on MOT

Since the MOT was introduced – and especially in recent years – there have been major advances in vehicle technology. These include the development of hybrid and electric vehicles; rapid progress in systems that automate actions such as parking or providing information to the driver.

It is therefore appropriate to consider whether changes need to be made to ensure that the system for assuring that vehicles are roadworthy remains fit for purpose.

The consultation currently taking place is seeking views on changes to roadworthiness testing. The first part considers the case for changing the date at which the first MOT is required and proposes that the date of the first MOT is changed from 3 to 4 years and some related changes.

The second part of the consultation asks broader questions about the nature of the MOT – what is tested and how and the frequency of tests. The DfT is also asking whether there are other approaches that could achieve our road safety and environmental objectives.

Read the CO Research Trust's response in full below.

MOT Consultation Response

Download Response  CO Research Circle