I can’t find the answer in any of the reference material I have so I put the question to y’all.
What is a single slip and double slip?
I am by NO means an expert[bangedhead], but let me try and answer your question. Both of these slips are turnouts that are shaped like an “X” on its side. A double slip allows a train entering into either of the legs of the “X” to proceed straight through or to one side. A single slip may only allow one of the entrance legs to make that transition to either of the opposing legs. Wait and see if anyone corrects me. but I think that is correct. Hope this helps you out!!
Just to be sure, check with my best friend - GOOGLE - and do a search on slip switches…he should help you out with a definition! [swg]
Think of a crossing, (or diamond in RR terminology) crossing at acute angles. A crossing only allows trains to cross the opposing track. Now think of a crossing, which allows one train to cross just like a crossing, but, with the option of the train diverging on the opposing track. This is a single slip. If the crossing were to allow either crossing or going out on a diverging route for all four legs of the crossing, then it is a double slip. These things are much easier to see and understand how they work, than to talk about and explain. If you have Walther’s Catalog, look up under track.
The reason for slip switches was to allow changing routes in very close quarters, such as yards and near terminals.
I drew this diagram for a different discussion, but the schematic version of the two specialty tracks should help illustrate what the others have already said.
If you want to see the original discussion, here is the link. It was about the difference between a double slip and a double crossover, but you may still find it interesting.
http://www.trains.com/community/forum/topic.asp?TOPIC_ID=19576