A tougher and updated MOT has come into force in Britain to improve air quality and make roads safer.
Diesel cars are now subjected to tighter smoke limits, while new fail categories state when a vehicle should not be driven until a dangerous defect is repaired.
A number of components and functions will be tested for the first time under the refreshed regulations.
Gareth Llewellyn, chief executive of the Driver and Vehicle Standards Agency (DVSA), said: “DVSA’s priority is to help you keep your vehicle safe to drive.
“You can start to look forward to cleaner, safer vehicles, with greater clarity on any defects identified by the tester.
“A properly maintained vehicle should have no problem passing the new MOT.”
The new rules could lead to expensive bills for people who have previously taken their cars to unscrupulous garages where DPFs have been removed because they are costly to replace when faulty.
New DPFs often cost more than £1,000, which is more than the value of many cars on the road.
Among the checks being carried out for the first time under the new regime are:
- if tyres are obviously underinflated
- for fluid leaks posing an environmental risk
- reverse lights on vehicles first used from September 2009
Motoring groups have expressed concern that many drivers are confused or unaware of the new test.