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Originally Posted by lrt's friend
I really wonder whether 8 minute frequency is achievable without full double-tracking. We are always constrained by the longest section of single track. By the time we get to double tracking Walkley Station, all the low hanging fruit are gone. After full double tracking, we might as well run trains every 5 minutes and make it a real trunk line. This will probably take decades, so the need may already be there, plus, we can actually start serving the inner suburbs properly.
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The two most expensive portions to double are the Dow's lake tunnel, and the Rideau river bridge. Both of these could be avoided for a while longer with sufficiently high-speed switches.
Both the bridge and the tunnel are some of the line's fastest portions, but the real slow downs are when it comes to crossing the switches at either end of Carleton (and on whatever the next switches on the opposite sides are).
I think if you double Walkley, Mooney's, and Carling leaving the bridge and the tunnel as the only single track sections North of Greenboro. Your main constraint would then be Greenboro but that's, among other things, trivial to double.
Imagine two trains meet at a doubled version of Carling. Meanwhile on the other side, two trains have met at a double version of Mooney's.
- Southbound train departs Carling, Northbound departs Mooney's
- Both trains travel line speed (~50-60km/h) and as they approach the tunnel/bridge they switch onto the single track without slowing down (high-speed switch!)
- They continue, at speed (or possibly faster) to Carleton, and thanks to a combo of higher speed switches, and PTC allowing them to continue into the station without slowing down so much, they pull into the station much like any fast train does
Meanwhile, the other trains that were headed the other way would have had to pass the next set of trains at either Gladstone/Walkley or Greenboro/Bayview.
Come to think of it, Greenboro may need to be doubled.
But I'm not a rail planning expert. I remember Joseph Potvin mentioning some open source rail network simulation software at some point. Maybe I'll try to learn how that works... Edit: it's called MATSim
https://www.matsim.org/
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You have to wonder about this city's decision making. Aren't they talking about quadruple tracking to provide both UPX and service on the GO Kitchener Line? And there is no question, that to provide even 15 minute frequency, they need to double track the Stouffville line. We figure we can do more with less, but there is a limit. In this case, the number of passing tracks may be the death knell of service beyond 10 minutes. At that point, it is not just the length of double tracking, but the number of passing tracks that will be the constraint. We cannot physically manipulate more than 4 trains on the section of track from Greenboro to Bayview with only 3 passing tracks.
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There's a big difference between the operational needs of a 12-car true-heavy-rail train and whatever it is you'd call what we have on the Trillium Line. It takes significantly more time to accelerate and stop one of those trains which makes any stopping/passing a lot more time consuming.
If we had some.. regional rail system running, we'd absolutely need 3-4 tracks, but 2 with a
few (as in, 2 or 3 short and fast ones) pinchpoints can be manageable.
Having PTC should help as well since it'll allow trains to push towards the speed limit more often. Technically PTC should allow for ATO, even on a fixed-block system, but I doubt that will be implemented.
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Great pictures folks!
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