The problem with trains isn t starting them it s stopping them once you have. So how do you stop a train Steel tyres and steel track don t make for very good stopping power. Slamming the brakes on wont stop it, all you will achieve is a skid which lasts for a good long distance and locked wheels which end up with flat parts on the tread and a damaged track. What we need to do, is to progressively retard the rotation so that the force involved is spread over greater time. We achieve this on a railway in several ways.
Lets look at the factors involved.
This would then result in either the train not stopping when expected or even accelerating on a gradient with the brakes on. The second factor is the track itself, you may think that steel is steel is steel. This would be far from the truth. In different weather conditions steel behaves very differently. Steel becomes greasy when it gets wet, this is because it is partly porous and retains any oil or grease that has transferred to it and as you all know oil floats on water.