Since the beginning of 2007 newly authorised locomotives or other traction units in Europe have been given a 12-digit number, as required by the European Railway Agency's CR OPE TSI. This makes the locomotive clearly identifiable from an EU-wide list of registered railway vehicles and follows the rules introduced by the UIC Code of Practice 438-3, Identification marking for tractive stock. A complete number comprises 12 digits. Digits 1–2 are the type code, 3–4 the country of origin, 5–11 are defined by the country concerned, 12 is the check digit. It is followed by abbreviations for the country of origin and the owner of the vehicle. The EU CR OPE TSI required that by 1 August 2008 all traction units had to be registered and marked with their number. Existing locomotive numbers used internally were not affected.