That really depends on the exact traffic flow, the amounts of trains going one way or another. So it is hard to say.vanatteveldt wrote:Is there any loss of throughput in connecting the lower tracks going straight? It seems that if "most" trains are going straight, keeping the parallel tracks intact would help throughput, and I'm not sure how they would make the traffic blocks worse? (but my grasp of railroad throughput is pretty limited)
If the probability of trains taking each path is equally distributed then with my method the amount of throughput for a 4 track approach is the most efficient possible currently, because trains cross tracks only if really necessary and otherwise avoid crossings thereby also causing less traffic jams. Putting an additional track thorugh the intersection would only introduce an additional probabillity for additional delay.
If the probabillity is exceptionally off then there might actually be a chance that routing double tracks through the intersections might not result in as much of a penalty as it would if the probabillity is equally distributed.
If for example there are 4 parallel tracks and a small T-intersection crossing all 4 tracks... for let's say a terminal station where only one or two trains ever visit out of 50 traveling on the 4 parallel tracks or whatever then there might not be that much of a penalty doing it, given one does the signaling right.
If 10 out of 50 are going to use the terminal you will probably be noticing the effect already because every 5th train will be causing some others to wait and the waiting trains will themselves cause others to wait, etc. At some point it might be wise to change the layout to my proposal to minimize the amount of possibly affected trains that have to wait.
You surely heard about progressive signal system or synchronized traffic lights where traffic is bundled together in such a way that multiple cars going in a certain direction seemingly always have green lights when reaching the traffic light. With better signaling... and with that I mean "sensors" to check for trains (and where they are going) and making block signals work together with circuit logic one could create something like a system that "packs" and "channels" the traffic better than now. Then it might be possible to do bigger intersections because it might be possible to catch like for example 3 trains that want to go in the same direction, make them wait together and fire them off together in parallel rather than one after another in random order causing complete chaos and free for all scenarios. But something like that would require a lot of help from logic circuitry and sensors determining the actual state of the system to be able to make on-the-fly adjustments. But that's purely hypothetical and worth its own thread.
But just think about real life... if just ONE guy decides to make a left turn (if we are not in the UK) with his car on a main road with heavy traffic he is causing a huge traffic jam with cars piling up behind him and also on the opposite-headed direction if there is no way to evade. A little car just causing a huge mess. A huge, sluggish 40 ton truck with 20m length or more cars are even worse due to the introduced delays. And we are talking trains...
I wonder if there is a mathematical model for calculating something like that correctly, because I found nothing particularly useful when googling.
I only had an in-depth discussion with one of my former professors about the topic about 5-6 years back when we were talking about urban planing of roads/streets and stuff (I studied construction engineering so it partly falls into my business as well). There he tried to explain the problem to me in a rational manner and why urban planners nowadays try to avoid particular types of crossings and other things because they tend to become problematic over time depending on unforeseeable changes in traffic amounts (more and more people want to go by car causing more traffic) and also changes in path priority (like population distribution shifting from one part of the town to another due to migration or new settlements, etc).
The rest is experience with games like OpenTTD, Transport Giant, Industry Giant, Factorio, etc. as well as relying on the information of other people trying to find solutions to the problem. Which there pretty much are none other than eventually using bridges and tunnels. Without bridges/tunnels it basically is just shifting the problem from one location to another and on long term all parts will be affected again.
