clutch or gearbox. Maintenance that is necessary for the reliable and efficient operation of the vehicle – but not its safety – forms part of a service inspection that is recommended by manufacturers, but is not a legal requirement for operating the vehicle on the public highway. Items such as the windscreen, wipers and exhaust systems are tested for condition and operation. Windscreen wipers will fail the test if they do not adequately clear the windscreen when used in conjunction with the washers. The exhaust system, in addition to checks on its condition and security, is tested to ascertain whether it is obviously louder than another vehicle of the same make and model with a standard exhaust system fitted. Dismantling of any part of the vehicle during the MOT test is strictly against test regulations, making the assessment of corrosion or worn components in certain areas on certain car models very difficult to determine accurately. As the MOT is only an inspection for roadworthiness at the time of test, the inspection of most accessories is not included. One exception is tow bars: their condition and their attachment to the vehicle is now included in the MOT. Lighting exemption A vehicle that has no front- and rear-position lights fitted or has had those lights permanently removed, painted or masked-over is exempt from the lighting sections of the MOT test. An advisory note will be provided on the VT32 as a reminder that the vehicle should only be used during daylight hours and not used at times of seriously reduced visibility. This is sometimes incorrectly referred to as a "Daytime MOT", but there is no official distinction. It is the Road Vehicles Lighting Regulations that prevent an unlit vehicle being used on the road after dark, not the MOT. Historic (classic) vehicles exemption A vehicle is exempt from the MOT if it was first registered more than forty years ago and no "substantial changes" have been made to the vehicle in the last thirty years. This includes vehicles previously exempted on the basis of being first registered before 1960. A vehicle alteration is a "substantial change" if the technical characteristics of the main components have changed in the previous thirty years, unless these fall into the acceptable alterations category. Different rules apply to large vehicles. An exempt vehicle must be roadworthy. Re-tests When a vehicle fails the MOT test it can be