Abstract
Leaf fall during the autumn season creates low adhesion problems on the railways. Traction gels are used to prevent low adhesion, but very little testing has been carried out to assess their performance. Views on their effectiveness vary and their usage is inconsistent across the UK network as a result. This work developed a range of full-scale laboratory and field tests that can be used to assess traction gel performance. The outcomes can lead to increased industry confidence in their ability to mitigate low adhesion, as well as in future product development. It was shown that as a wheel passes over a puddle of traction gel on a rail head, that the gel element is squeezed away leaving the solid particles behind, pick-up on the wheel of particles was also evident. Traction gels were shown to increase traction in full-scale laboratory friction tests in dry and low adhesion conditions. Field brake tests showed that braking was effective in low adhesion and dry conditions with traction gel applied, matching the laboratory test results. The traction gel was also shown to remove a leaf layer, artificially produced by running a DMU over leaf material on a test track. Subsequent work should validate the results on a working railway line during the autumn season.
Highlights
Leaf fall on the railways causes low adhesion issues every autumn due to increased journey times, wheel flats, station overruns and safety issues
The full scale laboratory testing showed that traction gel was able to increase the traction coefficient compared to both a dry and wet contact
A realistic low-adhesion layer could be created from leaves using the FSR, similar to that created in the field testing in this work
Summary
Leaf fall on the railways causes low adhesion issues every autumn due to increased journey times, wheel flats, station overruns and safety issues. Leaves are blown or fall directly onto the railway and stick to the railhead in wet conditions. Chemical reactions between the leaf material and the steel take place[1,2] and black material is formed which can be pushed or washed down the railhead with subsequent wheel passes and rainfall. As well as the bulk leaf, a black, sticky, and paste-like material has been washed down the railhead and is present both in and outside the contact band. The photographed railway line is irregularly used and in this case the leaf seems to be intact, the number of wheel passes that have occurred over this leaf is unknown, but there is a clear difference between the leaf properties in the centre of the leaf over the running band, as opposed to the edges of the leaf
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