Updated MOTs to include air pollution testing improvements

Proposals to update MOT testing, including improvements to the monitoring of emissions to tackle pollution to bolster the environmental efficiency of vehicles, have been published for consultation by the government.

Under the proposals, the Department for Transport (DfT) has outlined plans that would require MOTs to check that diesel vehicles are fitted with a diesel particulate filter (DPF). This is a device fitted within the exhaust pipe to filter particulate matter (PM2.5) pollution from the exhaust gases. 

According to the document, poor maintenance of these filters can affect performance and ultimately lead to repairs, which it says has led some diesel vehicle owners to remove their filters.

The consultation notes that this is “both illegal and will lead to excessive air pollution”, with removal of the filter associated with a 10,000-fold increase in the number of particulates emitted by the exhaust.

Although the current MOT rules includes a provision to fail a vehicle where the DFP is not present or inoperative, the consultation document notes that this is “not easy to determine on many vehicles”. 

Therefore, the Driver and Vehicle Standards Agency is currently trialling particulate number testing, which is a new way of testing tailpipe emissions to determine if the filters are present and working. The consultation is calling on stakeholders to share their views to inform the implementation of this testing.  

The consultation also notes that the current MOT test does not include a direct examination of the performance of nitrogen oxides (NOx) control systems. The department is therefore calling for views or research on methods that could be applied within the test to assess the performance of these control systems on both petrol and diesel vehicles. 

Another area open for consultation is regarding the World Harmonised Light Vehicle Test Procedure (WLTP), which seeks to assess how much carbon dioxide (CO2) a vehicle produces before it can be legally sold. 

However, the document notes that previous evidence has demonstrated that the CO2 emission figures produced during the lab-based tests can “vary significantly” from the real world CO2 emissions and that this gap has been found to get worse over time. 

The department is therefore seeking views on whether the monitoring and recording of fuel/energy consumption data can be done via the MOT. 

The consultation also highlights that the lack of check of the emissions or performance of hybrid vehicles during MOTs is a “significant issue”.

The document says that more information would be “welcome on how these vehicles can be tested” with the department noting that it is “committed to working with manufacturers and other stakeholders to find practical solutions to this problem”

The consultation will close on 28 February and is available to view here.