Fewer cars are failing their MOT test for exhaust issues, despite the introduction of new, more strict, regulations.

Data from Protyre reveals that there has been a 21% decrease in the proportion of cars that failed an MOT test in the last year.

The DVSA introduced new legislation on May 20, 2018, affecting diesel cars with diesel particulate filters. These cars will fail the test if any visiable smoke is seen coming from the exhaust tailpipes.

David Sholicar, Protyre’s national retail operations manager, said: “The fall in the proportion of MOT fails attributed to exhaust issues at first appears surprising as the new MOT test includes stricter regulations on emissions from diesel cars. The test changes also mean that it is now law that any car with a diesel particulate filter automatically fails its MOT if smoke is visible from its exhaust.”

Analysis from Protyre shows that only 7% of diesel vehicles that failed their MOT test did so because of issues with the exhaust – compared to 11% of all vehicles overall that failed their MOT test because of exhaust issues.

These new figures come despite overall increases in the raw number of MOT tests that failed because of exhaust issues shown in the most up-to-date DVSA figures.

“One reason for this reduction is down to the reduced popularity of diesel cars and nationwide year-on-year decreases in sales of new diesel vehicles in recent years of up to 20%. However, the data also shows that the decreased proportion of MOT fails (despite an overall increase in numbers) is likely down to stricter criteria on other components,” Sholicar added.

The data also shows a 7% year-on-year increase in the proportion of MOT tests that failed because of warning lights and a 7% year-on-year decrease in the proportion fails because of faulty brakes.

The proportion of MOT test fails attributed to failed suspension compontents decreased 11% and the proportion attributed to faulty car lamps also decreased 8%.

The new MOT test includes new testable items related to braking device performance, the daytime running of lamps and the Engine Malfunction Indicator Lamp.

In the year since the changes to the MOT test, faulty suspension was the most common reason for a test fail, followed by brakes, lamps, tyres and obstructions to drivers’ view of the road.