My little Ross Run N logging module has a switchback, but that's mostly because the prototype Ross Run line of the Hickory Valley had two. I don't know the grade, but my model is 4.5%. The prototype map is here: http://gustafson.home.westpa.net/wdmap3.jpg I wanted something that specifically could highlight the right-hand side of an Atlas Shay pushing cars uphill. The module is only 42" long so the design of the switchback had to cheat in several areas. The lower tail ducks in a tunnel and is part of the storage and return loop, the upper tail can be extended BEHIND the existing HVRR lumber mill module to gain additional space. But for switchbacks, I think the all-time champ in PA was the line uphill on the Bellefonte & Snowshoe line that was taken over by PRR. It was primarily a coal-downhill line but it had SIX SWITCHBACKS to get from the top to the bottom of the hill. It was so bad that I've heard this is what started the 'deal' between PRR and NYC to use the West Branch Valley trackage rights instead of the horrible PRR alternatives to get coal out of the Clearfield district. Take a look at this mess, upper LH corner. I have this up on my office wall as the 'worst railroad design ever'. I've seen some photos of this somewhere online but can't find them. http://historical.mytopo.com/getImage.asp?fname=blft09nw.jpg&state=PA One thing I disagree with is that the switch should be flat. What I see is that the 'bottom' switch stays on the ascending grade, and the 'reverse' switch vertical curves up. I've never seen anything on the prototype or at Cass to indicate that the switch has to be on the flat. On Cass, and on some other switchbacks, I've observed that the tail track will continue to climb uphill. Ive suspected that that's a deliberate design to help in case of runaway.
