This project deals with situations where the track noise contribution is important in the global pass-by noise, i.e. surface rail transport with speeds between 20 and 200 km/h. In order to obtain the highest possible impact with the resources available, Quiet-Track will focus on very effective track based rolling noise mitigating solutions for trams, regional trains, surface metro and trains in an urban environment with direct application possibility to conventional railway tracks outside the city.
Background to the project
- The European Noise Directive (END) requires noise maps in the cities, including the noise coming from all surface rail transport and action plans with solutions to reduce the noise hot spots.
- The rolling noise or wheel-rail noise is the most dominant railway noise source for vehicle speeds from 20 to 200 km/h. Below 20 km/h, the vehicle engine and ventilation noise is dominant, above 200 km/h the aerodynamic noise is dominant (high speed trains).
- For normally maintained surface rail transport vehicles (tram, regional trains, conventional trains), the track noise is dominant over the vehicle noise.
- For most freight trains wheel noise dominates, the rolling noise will not be reduced by track related measures (e.g. rail grinding has no effect on the rolling noise).
- Acoustic rail grinding is by far the most effective track based method to reduce rolling noise for non-freight surface rail transport, noise reduction of 10 dB(A) are feasible.
- Efficient noise mitigating solutions exist along railway lines but many of these solutions (e.g. noise barriers) cannot be applied in city (street) environment.
- Most existing noise mitigating track solutions used today (such as rail dampers) have only a small noise reduction performance (average 2 dB(A) reduction).
Expected Results, End Users and Exploitation/Dissemination Plan
A procedure for noise monitoring and for determining the TDR’s of embedded rail will be developed and validated in the network of DL. A procedure for correcting the TDR’s in function of the temperature (or in function of the temperature related rail stress) will be developed and validated.
The rolling noise calculations will be carried out with the W/R NOISE program. A procedure for calculating the low frequency noise emission below 250 Hz and propagation will be proposed and validated for two selected reference track systems (one embedded and one with discretely supported rails on sleepers in a ballasted bed.
The effect of acoustic grinding will be evaluated experimentally. The monitoring will be used for establishing the relationship between rolling noise and different types of rail wear. With the monitored rail roughness data and noise related rail wear data, a Maintenance Tool will be created.
Four different development directions have been identified:
- Direction 1: combination of existing solutions. The individual performance of many existing solutions at the track level is not very good. In Quiet-Track, existing solutions will be combined to yield a global performance of at least 6 dB(A).
- Direction 2: reduction of rail roughness growth rate. Solutions will be developed which are based on the concept of reduced rail roughness growth rate. The first type is a very resilient highly preloaded rail fastener, which can be used on a sleeper or directly on concrete. The second solution is based upon the use of geometrically very stable tracks, which require far less correction (tamping) than conventional tracks.
- Direction 3: low noise embedded rail. Experiments have shown that a rail which is completely embedded within a sand bed yields noise reductions of up to 10 dB(A). This track type will be optimised for its noise mitigation performance.
- Direction 4: low noise rail type and hardness selection. A procedure will be developed to select the optimal rail type in terms of minimal rolling noise emission combined with optimal wear characteristics taking into account tangent track and curved track.
Noise Management Tools
The output from the Maintenance Tool in combination with an application of a noise mapping software and the yearly maintenance costs of Optimized Acoustic Grinding and Acoustic Wear Removal and the whole life cycle costs of the network will be investigated and contrasted with the monetary benefit from the noise reduction along the network.