I'm pretty sure that Alna Center was single track throughout the original railroad's existence. The passing siding was added by the WW&F Railway Museum. While not original, it does serve several purposes including the run-around (now unneeded), staging for ballast delivery, special events such as the Ice Cream Social, etc. If trains were ever originated from both 218 and Sheepscot, it would make a good meeting point. Some people have discussed offering both a long ride (Sheepscot to 218) and a short ride (Sheepscot to Alna Center). In short, the siding has proved so useful I doubt it will ever go away.