Ricardo’s Track Consultancy team were closely involved in a trial on the UK network throughout October 2019 that could improve future service performance in adverse autumnal conditions.
Leaves that fall on rail lines in autumnal months are quickly crushed under the wheels of passing trains, leaving a hard residue on the railhead. When this is combined with a little moisture (morning dew, for example) it results in very low adhesion between wheel and rail, adversely affecting train braking and acceleration performance.
A response long used by the industry has been to deliver sand from the vehicles directly onto the rails to improve wheel/rail adhesion. This latest trial, however, sought to see if that approach can be improved upon. It will build on research initiated by the UK’s Rail Safety and Standards Board (RSSB), and undertaken by Ricardo, looking at whether it was possible to optimise the distribution of sand to further enhance stability on wet and slippery tracks.
The initial research in 2017 examined various permutations, such as whether trains travelling at higher speeds require higher quantities of sand, or perhaps the number and distribution of sanders along the rake had a positive impact.
This RSSB-led project demonstrated that Double Variable Rate Sanders (DVRS), which actively target sand delivery at axles which are experiencing slide, could provide an assured 6%g deceleration, even in very poor adhesion conditions. Neil Ovenden (Chair of the Adhesion Working Group) said “I think this is the single biggest step forward in adhesion management in the last 20 years”.
However, a further step - an in-service pilot - was necessary if the industry was going to be encouraged to adopt DVRS.
The autumn 2019 trials were designed to put the earlier research findings to the test in a real-world environment, using class 323 units on a local line in the West Midlands that was to be closed each Sunday in October.
The expectation was that the trials would provide further demonstrate that DVRS will significantly improve low-adhesion braking performance. It will also be an opportunity for drivers to experience the technology in a safe environment and to get their feedback on implications for their driving.
Testing DVRS with Class 323
After an initial feasibility study looking at the technical aspects of the upgrade, Ricardo drafted the technical requirements and functional specifications. Our role as technical lead included: refining the interfaces, undertaking the cross-discipline engineering, coordinating the suppliers and managing the approvals / engineering change processes, as well as installation of instrumentation to allow remote monitoring of the performance of the upgrades.
"The testing programme has progressed really well," reports Liam Purcell, Principal Consultant, Ricardo, who was been closely involved with the project's development.
"This was a technically complex modification, requiring multiple interfaces with the vehicle's brake control, electrical and pneumatic systems, in addition to the physical and structural aspects associated with upgrading the sander hardware. But we delivered two upgraded trains that could be monitored throughout Autumn 2019. We have subsequently received excellent feedback from the train drivers, with the results showing that DVRS almost halves the braking distance in very low adhesion conditions”.
The UK network currently introduces an amended autumn timetable on certain routes that introduces longer gaps between services and requires that drivers reduce speed to allow for longer stopping distances and prevent trains overrunning station platforms. The new technology is expected to pave the way for vehicles equipped with DVRS to get much closer to performing as consistently in low adhesion conditions as they do at other times of the year.