05-05-2022, 03:17 AM
(This post was last modified: 05-05-2022, 03:18 AM by danbrotherston.)
(05-04-2022, 05:31 PM)tomh009 Wrote:(05-04-2022, 12:51 AM)danbrotherston Wrote: That's interesting. For context...a GO train will traverse the 3.6 km in just over 2 minutes at 100km/h (a moderate top speed for GO trains--they can go much faster but usually don't).
How often are Kitchener line trains arriving within 2 minutes of their scheduled arrival time? If they arrive outside this scheduled arrival time they will delay the outgoing train.
Passing tracks can work, but they are very fragile to any scheduling issues like one might have when sharing with freight.
A 2.6 km passing track should be long enough for most (all?) freight trains as well.
Yeah, it should fit freight trains as well, although AFAIK the freight conflicts are generally not on this segment of the Kitchener line, which Metrolinx already owns.
My point was that, for example, a Kitchener bound train may be delayed by a freight train near say Georgetown, and then be arriving in Kitchener 10-15 minutes late. This is a common occurrence. So now, the train OUT of Kitchener cannot depart until 15 minutes late, because it must wait till the train coming into KW reaches the passing segment.
Even worse, unless there is 15 minutes of slack in the schedule somewhere else, that delay is going to continue to cascade through the rest of the day, possibly putting trains in more conflict with other scheduled services and getting delayed further.
As for using the passing segment for a freight train, that's possible as well, but it would be difficult. Freight is slow and adheres poorly to schedules, so it may end up blocking the passing segment for a long time. Which means GO trains wouldn't be able to use it and it would be more difficult to schedule around.
Obviously you can solve these challenges with MORE passing segments, but at a certain point, you should just build a double track line.
I *do* think there is an interesting inversion of thinking that nobody really talks about which is the concept of a double track line with choke points. I'm not sure how this impacts scheduling, but if you widen the track to double tracks everywhere except the most expensive areas (bridges, tunnels, downtown) can you achieve most of the benefit of double track, with a fraction of the cost? Or do you really lose most of the benefits. I'm not really sure, and I don't think anyone can really answer the question definitively without actually studying it, scheduling is another problem that humans aren't very good at (mind you, neither are computers). FWIW...there is a BRT line in Gatineau that uses this concept. It re-uses an old single track railway bridge to cross the...Gatineau? river. Buses arrive and must wait for the bridge to be clear of oncoming traffic before proceeding. FWIW...again, this is something that works better when you aren't sharing with freight trains.