Increasing Line Capacity With Passing Loops

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    So I’ve been watching a few videos on YouTube where users consistently are doubling the line right along the entire length of the line. There are a couple of reason why you wouldn’t want to do this in the early game:

    1. The cost can be prohibitively expensive and, in the early game, you need to keep construction costs down so that you can use the money to ensure your lines are as efficient as possible.
    2. The maintenance or running costs would effectively mean you’re paying double to maintain the line.

    I want to introduce a new concept to these people whereby you can increase your line capacity (ie run more trains, more frequently) without having the extra costs associated with doubling the track along the entire length.

    These are called passing loops. Please consider the following diagrams:



    In Figure A, you’ve created a passing loop and you have two trains, both at either end of the line. The passing loop is signalled in such a way where it allows uni-directional travel (ie they can only go one way along the line), so that if the red train arrives at the loop first, it will wait until the green train arrives at the loop and hence clears the section.

    In Figure B, you can see that now both trains have entered the protection of the signalled block in the loops. Note that in order for this to work properly, you must not place any signals anywhere else on the line outside of the loops unless you have more passing loops further up or down the line. However, you’d still only place signals within the loop, to create an area where trains can wait safely.

    In Figure C, you can see that both trains have now passed each other and can proceed safely to their destination.

    All arrows indicate direction of travel.

    It’s important to note here that if you have two trains running on the line, you will require 1 passing loop somewhere along the middle of the line. If you have four trains running, you will require 2 passing loops at a third interval on the line. So essentially, once you have two trains running, for each additional train you’re running, you will require an additional passing loop along the line. At a ratio of 2 trains to 1 passing loop, so 8 trains will be 4 passing loops. Once the line is running effectively, and returning a healthy profit, you can then consider whether you’ve reached the capacity of the line and it is worth doubling the line and hence allow block signalling to control the number of trains along the length of both lines.

    Anyways, I hope this helps you understand how passing loops work and how effective they can be at keeping costs down but maximising on capacity and hence the frequency of trains you can run along the line.

    Any questions, comments or suggestions please feel free to post below.


    how can I place uni-directional signals?


    You place the signal, then click on it (or its icon) and click the “One-Way” button. Note that it’s important that you place the signals on the outside of the line, as I’ve shown in my diagrams.

    • This reply was modified 9 years, 6 months ago by Steve.

    lol, thanks!  Makes things a lot easier, ..


    What Steve has suggested here makes sense, being an avid train simulator user, this is the best answer for creating more rail traffic, especially in the early stages of the game, when less goods will need transporting. This is how railways were developed in the beginning.


    @fuji You’re most welcome ūüôā


    another question: what if I have 3 parallel tracks? how could I place a signal “outside” the middle track?


    This is actually exactly how our King’s Lynn to Ely (UK) line works, the actual passing loop is a 2 track station¬†with the left track the¬†southbound line (to Ely) and the right track the¬†northbound line (to King’s Lynn)¬†and between each station is a single line. I will be using this layout for my early stations and possibly freight stations.


    Ok with 3 parallel tracks the layout would be a bit different. You would ideally make it so that it would be easy for trains to pass each other no matter which direction they’re travelling so that you always have a free track for a train to enter from either direction. Tracks on passing loops should always be signalled uni-directionally, so you would have two tracks that would be signalled in the same direction, and one track signalled in the other direction.

    However, it’s worth bearing in mind here that passing loops should not need to be more than 2 tracks to allow trains to pass each other. If you’re approaching the need to add an additional line, then you need to think about doubling the entire line and allow block signalling to handle the additional capacity.


    So here’s a triple loop :


    Note that you have 2 free blocks with either option but only in one direction. You need to decide which direction is more important to have trains waiting in.


    @Neil-R yes, it’s very common to use passing loops at stations, given that the train needs to stop there anyway – it’s even more efficient!


    That is very good. Most people don’t know this and don’t even understand the concept of signals. Usually hard core users do this kind of things, so most users will continuing making double tracks.


    Here are some links to the OpenTTD wiki pages that explain some signalling and layout concepts very well. TF players should note that at the time of this post not all of the signal types mentioned are in TF:

    Signals overview:

    Advanced path signal layouts:

    Owen’s pages (tons of superb info ¬†here):¬†

    I tried making these into proper links but the forum keeps losing my post when I do that ūüôĀ


    Thanks for spreading the word, Steve. People need to learn this very easy and incredibly powerful “trick” for the early rails. I use it almost everywhere, unless I know ahead of time a network is going to be running multiple trains very soon (Like one I have with 4 passenger trains, 2 oil, 2 goods and 2 lumber trains all in close proximity of each other)

    Specifically the game uses what OpenTTD refers to as Path signals. Only place signals where you want a train to make a stop, never anywhere else. You’ll need to set these at intervals to create “sections” that let trains behind start moving again. It’s quite simple once you grasp the basics. ūüôā



    i’m wondering why you recommend to place signals at the beginning of a passing loop?!
    usually “entry” signals would be placed before the passing loop and “exit” signals at the end of the passing loop tracks.

    would that conflict with the signalling logic of train fever? i see a lot of people placing signals this way in lets play videos, often causing trains to stop in places where they shouldn’t stop and thus blocking switches.

    i would like to know what happens if you would signal a passing loop/station realistically like this example:




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