Optimising track curving rules to allow higher speeds
The existing rules governing the design of circular curves and transitions in track have remain unchanged for decades.
In some cases, the current requirements may have been defined based on empirical evidence. Also, they were set without the modern simulation techniques available today.
These rules are set out in Railway Group Standard GCRT5021 Issue 5 – Track System Requirements (GCRT5021). The review process for GCRT5021 provided an opportunity to do a fundamental review of the current curving rules. It also allowed us to propose changes that seek to optimise the design rules on curves.
Through the Strategic Partnership with the University of Huddersfield, we undertook an investigation to see if the requirements set in GCRT5021 remain suitable. We also wanted to see if these could be optimised.
We compared the existing standards and vehicle dynamics simulations to examine the impact of curving rules on:
- derailment risk
- wear
- passenger comfort.
The study specifically examined:
- rules on cant
- cant deficiency
- cant in tight radius curves
- virtual transition
- cant gradient
- rate of change of cant
- rate of change of cant deficiency
- vertical curves.
We’ve been able to make specific recommendations on harmonising limit values with the European Standard and on adopting a longer virtual transition length.
The recommendations made provide evidence that will, in some cases, facilitate higher speeds on curves. In turn, this will have a positive overall impact on system performance.
These suggestions are being considered for adoption in the newest release of GCRT5021. This will enable these changes on the GB network.