Lift-over crossings as a solution to tram-generated ground-borne vibration and re-radiated noise

The operation of trams close to sensitive buildings can lead to concerns over ground-borne vibration and re-radiated noise. Vibration generated at the wheel/rail interface propagates through the track structure, through the ground and into buildings, where it may cause disturbance as perceptible vibration and/or re-radiated noise. This paper presents work undertaken to solve a re-radiated noise problem within the auditorium of the Royal Concert Hall, Nottingham, UK. The hall is situated alongside a crossover between two tracks of Nottingham’s Express Transit tramway. Initial measurements established the dominance of re-radiated noise over airborne noise. Simultaneous noise and vibration measurements were then used to establish the relative significance of the impulsive vibration generated at the various rail discontinuities of the crossover, compared with the essentially continuous vibration due to wheel/rail roughness. The results led to the selection of a new ‘lift-over’ crossing, together with an improved design of switch, as the basis for solving the problem. The paper includes descriptions of the experimental methods, together with a summary of the results. The new crossover design is described and the results of the commissioning measurements are presented as a final demonstration of the new lift-over crossing’s performance.