This European Standard applies to testing of rails installed in track for detecting internal rail defects. This part of the European Standard applies to testing equipment fitted to dedicated test vehicles or trolleys. This standard does not define the requirements for vehicle acceptance. This standard is not concerned with production testing of rails in a production plant. The standard specifies the requirements for testing principles and systems in order to produce comparable results in respect of location, type and size of rail defects. This standard is not aiming to give any guidelines for managing the result of ultrasonic rail testing.