Back to snow and rails. Does the snow trigger track circuits and cause track circuit failures? Is the main cause of infrastructure failures down to snow in the points.
Snow itself is a poor conductor and thus will not cause the track circuit to fail. Thawing snow, which produces water, and situations when water freezes can lead to scenarios where track circuit current can leak to earth, or in much rarer cases, cause a track circuit failure. During very heavy rainstorms it is not unusual for track circuits to fail when the water causes a temporary short circuit.
Turning now to points, it is not the snow that is the principal cause of points failures. What happens is this.
Snow falls and lies on the closed switch rail. The points are operated Reverse and detection is normally obtained because the point heater has kept the flangeway clear. In the interim, the snow that laid on top of the closed switch rail, which of course is now the open switch rail, will have fallen into the flangeway. If the points are then normalised, the snow is compacted, turns to ice which then by hydraulic properties prevents the switch rail from closing up again. Normal detection is now lost until the ice is removed or evaporates under the warmth from the point heater, UNLESS this occurs towards the heel of the switch where there is no heater and a very narrow flangeway clearance.
In the worst scenario, whilst motoring from Normal to Reverse, snow falls into the gap between the stock rail and the open (now closing) switch rail thus preventing the points going Reverse. The Signalman then cannot obtain Normal for the same reasons as posted above when he tries to Normalise them. Hey presto, points flashing OOC both ways and everything at a stand.
The old BR adage was that unless you have snowmen at a junction you set it up and left it straight., points heaters or no points heaters.
Keeping remotely located running junctions operating perfectly can be done - I proved this in the winter of 1984/85 - provided that the points are motored regularly and there are snowmen at them to continually clear up the large build up of snow on the closed rails. This however takes time and effort something that many people seem unable to want to exercise these days.
