A steel girder bridge was monitored in over to assess the suitability of the technique for use in a practical system. The bridge is relatively new and not expected to contain any fatigue cracks and was therefore ideal for obtaining signature levels for background noise arising from wind loading, traffic activity and the movement of welded and bolted connections.

The suitability of AE in bridge maintenance programmes is discussed. The features necessary for acceptance by the highway authorities are highlighted and a prototype system and strategy proposed.