Conventional railway switches guide trains from one track to another by sliding a pair of tapering rails horizontally. Repoint uses a lift and move mechanism, which includes a passive lock for when the points are in place. This is combined with a stub-switch type layout, which is said to offer advantages in many situations. The switch is further claimed to be ‘fault-tolerant’, continuing to work when two of the three actuators that control the movement of the points have failed.
Research published by the team in Railway Engineering Science describes the team’s development of a digital twin which has been used to show that the design meets and exceeds requirements for speed and performance.
The research investigated the performance of the switch using a novel method for simulating track system behaviour, which combines rail bending with physics-based models of actuators and control systems. The simulation scenarios included one of power failure to four of the six motors that drive the actuators, and showed that a single actuator is capable lifting and moving the points to the desired position.
Repoint was developed by Roger Dixon, Professor of Control Systems Engineering at the Birmingham Centre for Railway Research and Education (BRCCE).
Professor Dixon responded to a joint call from the Engineering and Physics Research Council (EPSRC) and the UK Rail Safety and Standards Board (RSSB) to look at ways of improving capacity on existing lines.
“While railway networks continue to carry more passengers and freight, building new track is always difficult and expensive, and increasing the reliability and exploiting the capacity of existing routes is generally the preferred option,” Prof Dixon said in a statement. “Although switches account for less than five per cent of railway track miles, they contribute to 18 per cent of delay minutes, and 17.5 per cent of delay costs in the UK.”
The team engaged with operators, maintainers and designers to understand the limits and issues with existing switch technology.
One of the most significant findings was the ‘single point of failure’ that is embedded in traditional switches and their detection systems, so the new switch incorporates fault-tolerant design.
Inspired by aircraft control systems, the team designed a switch that remains operational even when two out of three components fail.
Repoint actuation, which is at Technology Readiness Level (TRL) 4-5, has been tested at a test track, which demonstrated its compatibility and functionality with conventional switch rail arrangements.
The researchers are now seeking partners and funding to design and fully test the full repoint system including the actuators, permanent way (p-way), and interfaces to signalling.
Click here to read 'Rethinking rail track switches for fault tolerance and enhanced performance', published in 2016.