Are there any rough rules of thumb on how many passing tracks you need? For example, I have a 180ft single track mainline planned. How many feet of passing track should I have? Where should they be placed relative to the yard, staging areas, etc.? I have lots of track planning books but haven’t seen any advice on how to decide where to place passing tracks. Any ideas?
180 feet is roughly two and a half scale miles. Depending on your traffic density, I’d say at least two passing tracks (three will give you more flexibility, while four will make your mainline look like it’s double tracked). I’d keep your trains to 16 feet long or less as well; long trains are best suited for layouts with more than 8-10 scale miles of mainline.
That would depend on how busy your mainline is going to be. You have 3 scale miles but that is really irrelevant given that for most of us, the miles between towns are drastically compressed. Decide how many meeting points you think will need to keep traffic flowing. Also take into account whether yours is a freight only line or runs passenger traffic as well. Passenger trains (and priority freights as well) should not be force to spend much time on a siding waiting for an opposing train to clear the mainline ahead of it. If you have a real busy line, you might consider double sidings to allow 3 way meets. Trains in opposing directions would take the sidings while a third train with priority is allowed to pass. The best coverage I have seen of sidings is in John Armstrong’s Track Planning for Realistic Operation. It covers all types of meets and passes as well as track arrangements.
I have seen recommendations that you strive for two train lengths between sidings. For example if your average train is 20 cars long and they are mostly 40 ft cars then each car over the couplers is roughly 6 inches. Your train is 10ft long, add 2 ft for the engine and caboose gives you 12 ft (with a little fudge room). So you would want 24 ft between sidings. The sidings are 12 ft plus say 2 ft for the turnouts themselves plus 1/2 foot at each end to clear would be 15ft for each siding. 15 plus 24 is 39 ft. So for every 39 ft of mainline you would have one siding. 180/39 = 4.6 or 4 sidings. One of these would be with your yard, end staging loops would count only if they are part of your 180 ft.
Of course a big part of this process is adjusting to what you want to do. If you want to run 50 car trains then your sidings need to be about 30 ft long and you’ll have two of them. OTOH if you wants lots of meeting points then you’ll have less distance between sidings and maybe have 6 or 7, but you won’t have much single track. Or you could run 10 car trains with shorter sidings.
This is one of those compromise issues that we each have to decide individually based on prioritizing our desires and working within our space limits.
Good luck
Paul
That’s really rather like asking, “How long is a string.” The main determining factor is how you expect to operate.
If you’re a solo operator, running a single train, you might not need any passing sidings at all! (You will need runarounds for enroute switching, but that’s a different breed of cat.)
If you have a large, dedicated crew of operators (or are a Scoutmaster with a bunch of Merit Badge candidates,) you might need as many as you can get - including a couple of lap sidings to handle the occasional humongutrain that somebody is going to want to try.
If you are modeling a single-train-a-day shortline, your requirements will be very different from those of someone who is modeling a busy mainline, both in number and in length.
Without knowing your prototype and operating style, that’s the best I can do.
The question of the subject line is easier than the questions in the message.
The number of passing tracks needed is, a minimum of, one per train being operated simultaniously on a single track mainline.
I think the other questions have been covered by the other posters.
All of the above observations bring up good points. Basically you need at least one passing siding so 2 trains traveling in opposite directions can make a ‘meet’. One can go into the siding so the other can pass it on the main line. Two train length sidings would be better on an oval as with careful timing, you can constantly make a ‘meet’ every time you make it half way around the circle. More trains running at the same time? You need to add more sidings!
My layout haas a large ‘staging’ area that is double ended and can act as a siding. There are 2 other ‘train length’ sidings on the ‘on-stage’ part of the layout. I have less than 100’ of ‘on-stage’ trackage and run maybe 2 or 3 trains at the same time. Those 2 sidings and the staging tracks are more than enough for keeping thing ‘fluid’.
Jim Bernier