In my quest to model prototype buildings for my fictional railraod, I came across a set of decent blueprints for a "CPR Standard Interlocking Tower". I found the plans on the Canadian Pacific Historical Society website located here. CPHA: Canadian Pacific Historical Association Documentation Project You must register in order to search and access the on-line library however it is a painless process. Best thing...its free. I'm assuming that this little guy is pretty much the equivalent of a yard tower...except it appears to be smaller as the building itself has a scale foot print of only 12 x 12 feet. 30 feet in height, two complete floors with a ground level deck. Looking at my layout and the amount of real estate this guy is not going to take up any room at all. The question I have is, would this single tower at one end of the yard be built to handle all of the yard switches or would/could there be two at each ladder? We are talking about 20 t.o.'s in total. Just looking at it, I cannot see how it would be possible, as the personnel manning the tower would not be able to see over all of the freight cars to the far end at either side. Although, come to think of it, I may have a spot for it, where the ladders can be "seen" at both ends and a single tower scenario is possible. Also, it lookes like you want it in a place as well where the people in the tower are close enough to the track side so that they can converse with the engineer while in the cab. I plan on hitting the library tonight to get some more material for studying however, I'd like to hear some first hand information from you fine folks here. Thanks as always.