What is a runaround?

Suppose for a minute that you are running a way freight and you have to leave the second and third car in your train in an industrial spur that is facing towards you.

You can't just drive the train into the spur and leave the cars because you will trap the engine.

What you use is a runaround. A runaround is a section of track that essentially creates a loop in which the engine can "run around" the train to get in position behind it.

The engine then pushes the train into the turnout so that the cars it wants to drop are in position.

The engine then pulls back into the runaround. Circles back to the head of the train. And continues on it's way.

It should be pointed out that for demonstration purposes (and ease of drawing), I left the train on the main while I switched the siding. What is the more correct way would be to pull the train into the siding and use the main to run around the train. This leaves the main blocked only for short periods of time.

Another use of the runaround is at the end of a branch line. The train reaches the end of the line, disconnects, runs around to the rear of the train, reconnects and heads back the way it came.