Model railroaders are an optimistic bunch, particularly when it comes to layout design! To be more specific, overly optimistic when it comes to sketching in turnout geometry. We all do quick sketches to an illustrate a point. Trouble looms, however, when we stay with that approach as we delve more deeply into developing the design. When customers send me sketches of a concept they have in mind, almost to a person, the turnouts are drawn to dimensions that don’t exist in the real world. Can you say #3 switches! The problem is that turnouts, when drawn to actual size, are much, much larger than we would think. In addition, you’ll typically need a few inches of straight transition track leading into the ladder. I stick to a minimum “best practice” of nothing smaller than a number 6. The issue compounds when you combine a series of switches in a ladder. If you get too far ahead of yourself using a sketched design with grossly non-scale turnouts as placeholders, eventually you’ll be hit with the cold hard truth that what you had in mind simply won’t fit.
The first step in the right direction is to realize the problem exists early on. Next, move as quickly as possible to using templates of scale turnouts when doing your sketches. An excellent resource is Kalmbach’s “Model Railroader’s Guide to Freight Yards” by Andy Sperandeo.(Pg. 31 is particularly helpful).