Throughout autumn 2019, our Track Consultancy team were closely involved in a UK trial to assess how service performance could be upheld during adverse autumnal conditions.
Sanding as a track adhesive
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 small amount of 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.
The 2019 trial programme sought to see if the approach could be improved upon. It built upon on earlier 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 and provide further evidence that DVRS can improve low-adhesion braking performance. They were also an opportunity for drivers to experience the technology in a safe environment and to get their feedback.
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.