A lot of modelers will try to cram as much track as absolutely possible into their available layout space. There are a number of strategies that can be used to help maximize the running time of trains on a working layout, but one problem to watch out for while you're in the planning stage is a pinch point. This is a location where the tracks come so close together that it isn't possible to have two trains pass at that location at the same time. All the operation planning in the world isn't going to help as much as you might think, because at some point in an operating session, you will have two trains at the pinch point at the same time. So, before you start on scenery and as you're still working on the track, take out your longest rolling stock and run it on both tracks of the pinch point at the same time to find anywhere in that section where the cars touch. If it just is not possible to avoid clearance problems, it might be time to consider removing one of the two track sections that is causing the problem. You could also consider changing the pinch point to a section of gauntlet track to ensure that exactly one train will ever pass that point at a time. Oh, and before you go away thinking that this is only a problem on model railroads, the Seattle Monorail had a collision at a pinch point in its track in 2005.