Autumn leaves! At this time of year our thoughts turn to the massive problem of 'leaves on the line'. Every year Network Rail sends its 61 'leaf-busting trains', which clean the rails and lay adhesion modifier, all round Great Britain. Each autumn these trains cover a total of over 1.4m miles.
Scientists in the University of Sheffield have been studying the chemical process involved in turning autumn leaves into an unbelievably effective lubricant. They have discovered that the reaction between pulverised leaves and the iron rail surface produces a precipitate of iron tannate.
The next stage is to find a way to remove the tannins from the leaf coating on the rails. Experiments showed that a significant increase in friction coefficient would be achieved. The research paper concluded that "interventions can be designed to target the specific reactions or chemicals".
Recently RSSB (Rail Safety and Standards Board) hosted a webinar at which the Adhesion Research Group (an RSSB sub-group) described four different rail-cleaning techniques currently being evaluated and/or tested. These are Dry Ice (Cryogenic), Electrical Plasma Jet, Laser and Water. Scotland's Railway has already run both Plasma and Cryogenic trials, and is looking at bringing the Laser system to trial next Autumn.
The ideal solution would be on-train equipment which would remove the need for special trains which also take up valuable timetable paths.
For the Far North Line this might eventually mean that the problem of leaf residue will be solved much more cheaply. Currently, in the absence of leaf-busting trains, the work is done, as needed, by Network Rail SandRover road-rail vehicles, leaf fall teams and traction gel applicators (TGAs) on the track at vulnerable locations.
It will be interesting to see the outcome of all the experiments - let's hope this major headache for train operators can soon be treated.