Prototypical Question: Intervalls Inbetween Trains

LAST EDITED ON Jun-04-03 AT 08:17 PM (EDT)

I have a brief question regarding realistic scheduling of AI trains on some specific US routes I downloaded, namely at what intervalls AI trains would approximately need to be placed to get close to the prototypical situation.Dear fellow simmer community,Some questions and thoughts regarding North American RR operations have accumulated with me over the past few months of exploring US routes and rolling stock in MSTS, among them the following one regarding traffic density on some of the downloaded virtual routes. As I am not at all familiar with the details of operations and methods due to the fact that I grew up a little too far away from it, where I got used to different rules and railway operation procedures, I dare bringing some of these questions forward in a series of posts. I think that your answers might also be of interest to others, be it that they too are not familiar with North American RR, be it that they are new to the rails per se. The other topics are to be found in the following posts, which I decided to split in the sake of keeping each subject focused:Questions regarding Multiple Unit (MU) running of prototypical locomotives at http://www.train-sim.com/dcforum/DCForumID1/5339.html Questions regarding geographical assignment of prototypical locomotives at http://www.train-sim.com/dcforum/DCForumID1/5338.html Questions regarding prototypical speed limit policies for various train types at http://www.train-sim.com/dcforum/DCForumID1/5337.html Now for my question regarding realistic scheduling of my AI trains on US routes:Just a short question that sprang to my mind while working a bit on an activity. What would be an average intervall inbetween trains on a typical “heavily used” route such as Cajon Pass, the Conrail Indianapolis route, the CSX within NEC 4, etc? How frequently should one place a meet, a parallel AI run (on Cajon) etc?I admit that there is certainly a lot of leeway in the answesr, I’ll be happy just with a good guestimate stating some minima / maxima of what one would have to expect. With the many reports of railfanners out there, I’m pretty sure some of you folks can help me on this.

Again, thanks in advance! Lukas a.k.a Swissie

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RE: Prototypical Question: Intervalls Inbetween Trains, LAHDPOP, Jun-04-03, 08:53 PM, (1) RE: Prototypical Question: Intervalls Inbetween Trains, ace6879, Jun-04-03, 08:58 PM, (2) RE: Prototypical Question: Intervalls Inbetween Trains, mdeming, Jun-04-03, 09:53 PM, (3) RE: Prototypical Question: Intervalls Inbetween Trains, Dash9_Man, Jun-05-03, 09:21 AM, (4) RE: Prototypical Question: Intervalls Inbetween Trains, ace6879, Jun-05-03, 10:54 AM, (5) RE: Prototypical Question: Intervalls Inbetween Trains, Swissie, Jun-05-03, 05:22 PM, (6)

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Here's the short, non-technical answer.
Maximum train density (or frequency) is dependent on the type of signaling and control in use. In DTC territory (which is frequently dark), each train gets authority to enter a certain number of blocks. As long as that train holds that authority, no other train will be allowed into said blocks. So that's perhaps the most limited system. Trains will either be spaced several blocks from each other, or spaced closely, but running at slow speeds, to facilitate stopping at the end of the block to gain permission into the next one. Very inefficient, but still in use in some places here in the US today. Obviously, this system works best on lightly used lines.
With the TWC system, the territory can still be dark, however, the dispatcher has more options. He gives out authority for movement similar to DTC, but he's not bound by preset blocks. He can use mile markers, junctions, etc as the limits for track warrants. Also, as trains move through the warrant territory, they can give back chunks behind them as they clear them (instead of waiting to clear a whole "block" in DTC). So in TWC, its easier to run trains a little more closely together. Also, TWC territory can be overlaid with ABS signaling as a backup safety measure. A Clear indication is not authority to proceed, but it reassures you that the ABS block ahead is not occupied.
The systems that allow the greatest density of fast moving trains are ABS and CTC, and combinations of the two. In CTC/ABS territory, the ABS blocks may be as short as two miles each. So in theory, trains could follow each other at track speed, as long as they maintain a clearance of two blocks. If the distance between any two successive trains narrowed to less than two ABS blocks, then the following train would receive an Approach indication at the next signal, and start slowing down in anticipation of the next signal possibly being a Stop. Assuming the leading train keeps going, the following train can maintain the one block separation, and "run on Yellows" at a slower speed, or he can allow the train ahead to gain some ground, and return to running on Greens. Did I say this was gonna be short? Sorry, man. Got carried away. The REAL short answer is, look at the signalling. Trains can (and sometimes do) run as closely together as the signals will allow, including occupying the same block, running at restricted speed (rules vary by road). Assuming you have four 70mph intermodals running behind one another, they can run in a pack, keeping two ABS blocks clear between them, and scoot across the whole territory like that. Throw in a slow coal drag, and all bets are off. Now you've got to plan meets and run-arounds.Regards,
Pop

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Howdy, According to the rules, a train MUST follow 10 min. behind another train in dark (unsignaled) territory. In ABS signaled, CTC, or cab signaled territory, you must go on signal indication unless otherwise directed by dispatcher, or foreman in charge (in a work area)You can get right up behind another train IF you have a stop signal that is stop-and-proceed. (Usually a signal with a numberplate attached)What that means is, "after stopping at signal displaying stop indication, you may proceed at restricted speed, stopping short of other trains, men and equipment, or obstructions." (Quote right from the rule book)Hope this helps!!! Kelley D. Ellison



CSX A-Line Chief lighting engineer
NALW Lighting engineer
Dekosoft Lighting engineer

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Not really sure how closely this applies, but I lived near the UP/CNW west line for cose to 20 years, during the up years the train frequency ran on average 4 trains an hour. This was an extreemly busy line so a frequency quite a bit less than that would be realistic. On some of the less busy roads 4 to 6 trains a day would be realistic. This is an unscientific answer at best. On the CGW Eastern division 4 trains a day was normal, throw in an equal number of switch runs and that would be a good number.
Mike

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Was railfanning up in Colorado last year, and they were running coal trains (and a few manifests) 4 minutes apart.
-Sam

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Hey again, How rude!! LADHPOP had to put his over mine. sigh......WEll, both posts below mine are what I said about being on mailines with CTC and signals. TWC, DTC, etc. both specify how far, where and what NOT to get in the way of. You STILL MUST be 10 min apart PERIOD in dark territory. For reference, I am a pro railroader. Worked as a conductor. My railroa was ALL unsignaled dark track, and we operate under Track Warrant Control.Later!
Kelley D. Ellison



CSX A-Line Chief lighting engineer
NALW Lighting engineer
Dekosoft Lighting engineer

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Hi all,thanks a lot already for your differentiated answers! Already started to learn quite a bit of the "finesses". Thanks especially to you, Kelly, for the pro's view, and for LADHPOP for getting carried away and teaching me these comprehensive paragraphes on the different dispatch and signalling modes. Just for the record: Territory that is "dark" by default is something rather unfamiliar to me on Swiss roads, as all mainlines and almost all branches (I know of only one dark shortline of ca. 5 Mi length in the entire country) are signalled with automated blocks, dispatched mostly from regional control centres. There are restrictive rules on operating trains on "temporarily" dark routes, i.e. in cases of signals going down. These rules translate to something similar to what you quoted from the rules: The train is then operating under "visual rules", meaning that it must run at a speed that allows to stop the train at a distance which is half of how far the crew can see, or at 25 mph as an absolute max. speed for visual ops (IIRC). This kind of thing actually rarely happens, because if the signals go down due to a power supply problem, then the trains will do so too (99% electric ops). Lukas a.k.a Swissie

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