Squealing Noise in Sharp Curves in Athens Tram Network: a Synthesis of Mitigation Measures and Their Effectiveness

This article presents various operating systems, developed and implemented at the Athens Tram network aiming to reduce the airborne noise emitted in the sharp curves of the tramway. From the first days of the network’s operation (Olympic Games 2004), the problem of airborne squealing noise in sharp curves was revealed, generating complaints from residents in urban areas, especially regarding squealing noise emissions with peak levels especially during evening & early night hours. The problem was treated, initially, by coating the tracks with biodegradable lubricant, where friction phenomena were significant. The coating has been performed manually for some years by maintenance personnel of the network, providing suitable results as per the acoustic measurement program. Despite the fact that this intervention has produced positive results, alternative technical solutions were assessed, introducing water lubrication of rails by an automatic -quite simple -rail wetting system, containing sensors to detect approaching trams, water supply, timer, solenoid valves, pipes and common irrigation vaporizers, proven also to be successful and  economically viable. Furthermore within the Quiet City Transport project (QCity) under the EU's 6th FP on SUSTAINABLE SURFACE TRANSPORT  an integrated technology infrastructure for the efficient control of road and rail ambient noise by considering the attenuation of noise creation at source at both vehicle/infrastructure levels was developed and implemented in Athens Tram network with very promising results, indicating significant reduction in squealing noise emissions is also presented.