Lap Siding vs. Double-Length Siding

Lap sidings are often much more helpful than a "double length" siding and require about the same length of layout. This is thoroughly described in John Armstrong's Track Planning for Realistic Operation (Kalmbach) The reason for this is utility -- depending on train length, three (or even four) trains might be able to meet and/or pass flexibly at a lap siding. It provides two meeting points for almost the price of one.