If train is late its not because of “few leafs”. Wet, smushed leafs pack on the rails like film that slows down both acceleration and braking, because there is not friction, but there needs to be shit ton of them.

Ice effects supricingly little to acceleration/braking. Trains are so heavy that the pressure on the tracks melts the ice allmost instantly. Bigger problem is the snow, that starts to pack on parts of the train.

Id imagine big part why trains in Sweden and Finland stay on time is because train companies know trains move slower in certain times so they adjust the schedule accordingly.