Famously, British Rail issued a press release many years ago which blamed the suspension of rail services on 'the wrong kind of snow', which has become a shorthand for corporate uselessness. This was the 'right kind' because it could be cleared.
It wasn't a press release but a radio interview with a very senior and well respected operations director on BR who was asked why there were so many problems with the snow that was falling at that time. He stated that snow in this country is usually quite wet but the snow falling then was lighter and more powdery. It coincided with the introduction of push-pull trains running at 100mph+ where for half of the time the loco was at the back of the train pushing - the fine snow was whipped up by the train ahead and got sucked into the locos' innards. 25,000 volts and melting snow don't mix well and some major flashovers occurred, meaning that the trains had to be taken out of service to be repaired.
With more understanding of the problem, in recent years motors and other electrical gear have had enhanced snow protection, but you can't totally enclose them all the time as airflow is needed for cooling - motors get hot. A remedy is to run at reduced speed when the loco is pushing when snow is on the ground, or to always have the loco at the front (more difficult as terminal stations no longer have the facility to allow a loco to 'run round' its train.
The 'wrong type of snow' tag was invented by the media as the railways are an easy target. Problems over the past few days have been caused by ice rather than snow - just try running your track-powered G scale trains when there is ice on the rail as a result of a thaw and re-freeze, it doesn't work as ice doesn't conduct electricity although water does. Third rail electric powered trains have the same problem.
I speak from many years experience of trying to keep (real) trains running, including during the rare snow events in this country. Thankfully I no longer have receive the 'it's snowing, Guv' calls in the middle of the night but I have considerable sympathy for those that are out there trying to do their best when the elements conspire against them.
M
