Re: Derail and how common?

not sure where its going to put this in teh reply order but this is a picture of a fixed position flop over derailer.

it works like a re-railing frog in reverse, by pushing a run away car or engine over the rail heads and onto the ground . They are usually used on sidings and RIP tracks to derail anything that moves by itself before it can strike other equiptment or foul the mainline by splitting a switch or worse still becomming a runaway. I dont know if you've ever seen one before but when unlocked, the top half that would normally sit on top of the railhead, flops over to the inside of the rail giving plenty of room for car wheels and engine tires to pass over freely.
Another common type of derail is just a half switch with 1 diverging rail point if a car of engine goes into an open derail like this the guage eventually goes too broad for it and it drops betaeen the rails and again , comes to a stop.