This Technical Specification is applicable to buried or immersed cathodically protected metallic structures and influenced by a.c. traction systems and/or a.c. power lines. In the presence of a.c. interference, the criteria given in EN 12954:2001, Table 1, are not sufficient to demonstrate that the steel is being protected against corrosion. This Technical Specification provides limits, measurements procedures and information to deal with long term a.c. interference and evaluating a.c. corrosion likelihood. Even though short term interference can cause damage to buried pipelines (e. g. arc fusion), this Technical Specification does not deal with short term interference.