Wye

Signal, a photo by William 74 on Flickr.

In railroad terminology, a wye is a triangular arrangement of tracks, allowing three lines to connect. It's often used to turn trains around, allowing them to do a sort of three point turn. Usually there's a switch or signal at each corner as well.

This is one corner of such an arrangement, at the Illinois Railway Museum. It's guarded by this unusual, short position signal. The only other place I've seen similar signals is at Chicago's North Western Station...er, I mean Ogilvie Transportation Center. I don't think they're in use at Ogilvie, though, however I think they date back to CNW days.