The MOT test will change from Sunday, but many motorists say they don't understand the new rules.
While the new test will still lead to a pass or fail, faults will be categorised differently.
Defects found during the MOT will now be classed as 'dangerous', 'major' or 'minor', depending on the type of problem and how serious it is. 'Dangerous' and 'major' faults will result in a failed test, while those considered 'minor' will result in a pass, but should be repaired as soon as possible.
MOT testers will also still give advisories about items that should be monitored and repaired if necessary.
However, new research by the RAC has found widespread confusion about the changes.
Of 1,866 motorists questioned by the RAC, half (49%) thought that the new 'minor' fault category would lead to an MOT fail when it is actually a 'pass with defects'.
Meanwhile, 5% thought that a vehicle found to have a 'dangerous' fault would pass the test and 6% believed the same of a 'major' fault.
Three-quarters of motorists (74%) believe the introduction of the new 'minor' category, in addition to the existing 'advisory' notification, will lead to drivers not addressing these faults with their vehicles.
The RAC said that it supports the changes, but is concerned there could be some inconsistency in the way they are interpreted and applied around the country.
The new MOT test will also include additional checks, such as whether the tyres are obviously underinflated, looking for fluid leaks that pose an environmental risk, and checking brake pad warning lights and whether any brake pads or discs are missing.
It will also bring in stricter rules for emissions from diesel cars with a particulate filter, and some vehicles over 40 years old will become exempt.
In the RAC survey, 44% of drivers said they knew about the changes to the MOT test and 56% said they did not.
RAC spokesman Simon Williams commented: "It is important everyone quickly gets to grips with the changes to the MOT, and that test centres and garages do a good job of explaining the new fault categories so motorists understand correctly the severity of faults with their vehicles.
"Changes to the MOT that make vehicles using our roads safer are undoubtedly a positive step so we hope that testers everywhere interpret and apply the new rules fairly and consistently. The last thing we want to see is a lowering of MOT standards and an increase in the number of unroadworthy vehicles on our roads."
Were you aware of the MOT test changes?