Mitigation of noise emissions from vehicles passing bridge expansion joints

In the German project 'silent road traffic 2' a special sub-project for bridge expansion joint noise mitigation was launched. Travelling over a standard modular bridge expansion joint (lamella joint) with a vehicle creates a short noise impulse. The noise is the result of the vehicle's tyres striking the rectangular face of the expansion joint units and traversing the discontinuous surface profile. This noise can be annoying for those residing near the bridge. A reduction of the noise emission can be achieved by mounting noise reduction elements on top of the transition segments, by creating an even surface for the tyre to traverse, and still allowing the joint to contract or elongate as required due to the influence of seasonal temperature variation. Different surface elements for covering the transition segments with varying shapes and surface textures were tested in the tyre-road-interaction test-facility (PFF) of BASt. The surface elements had different shapes and surface characteristics; five were of a rhomboidal shape with three profile angles, one was 'mushroom' shaped, and two were of a sinusoidal shape. The surface elements were provided by two German manufacturers. The noises emission caused by traversing of a standard passenger car tyre was investigated for different velocities. All tests were carried out with two different spacings representing summer and winter position. It was found that a noise reduction of up to 9 dB could be achieved, when compared to conventional surface elements.