What is isolation?
Isolation refers to methods of protecting one line from the adjacent lines, e.g., in the case of loop lines that branch out from the main line at a station. A train or any rolling stock that is stopped on one of the lines while another train is moving through on the adjacent line should be prevented from moving and running over the points to the main line or fouling the adjacent line. There are several methods adopted to ensure isolation. Haye’s Derails (which guide the flanges of wheels over and across to the outer side of the rails to derail a moving vehicle), Scotch Blocks (which prevent points from being set for vehicles on the loop line to be sent to the main line), and similar devices are sometimes used (more so in the past – these are less common now). More commonly now, derailing switches (points that deliberately take the moving vehicle off the line and derail them) or points that lead to sand humps or sidings are used. Derailing switches or points to sand humps, sidings, etc.
