UK: In response to the collision which resulted from low rail adhesion at Salisbury Tunnel Junction in October 2021, all of South Western Railway’s Class 158 and 159 diesel multiple-units have now been fitted with Variable Rate Sanding equipment supplied by Siemens Mobility.
The variable rate control equipment is designed for ‘bolt on’ retrofitting to a vehicle’s existing sanding system.
It is triggered by the existing wheel slide protection system, and automatically uses live data on the train’s speed, brake demand and adhesion conditions to deliver sand at up to 5 kg/min to ensure rapid braking without the driver needing to take action.
Unlike traditional fixed rate sanding systems, VRS varies the distribution rate to suit the conditions. Siemens Mobility says this can reduce the braking distance by up to half, mitigating the risk of platform overruns and signals being passed at danger and reducing the development of wheelflats.
