GO Transit: Construction Projects (Metrolinx, various)

[Voltz]

WIth the Stouffville line, it's bound to be difficult to build the lowered corridor just north of Danforth Rd, there can't be enough space to build the new two track trench with another track running beside it, unless they take over some backyards.

 

[crs1026]

WIth the Stouffville line, it's bound to be difficult to build the lowered corridor just north of Danforth Rd, there can't be enough space to build the new two track trench with another track running beside it, unless they take over some backyards.

I can't fathom how they will do this. It's only 739 feet from the bridge at St Clair to the point where the new duckunder track will have to enter a tunnel underneath the LSE line. That's a huge drop if that track crossing under the LSE is to meet the electrification plate dimensions. We will see if this holds up as they design it.

It's also a tight squeeze to build a 2-track tunnel north to Danforth Ave. Looks like they may lay a diversion track right on Midland while they do the construction. In all that's more tunnelling planned than Scarborough has seen since the SRT replacement debate began.

- Paul

 

[crs1026]

One further discovery: It looks like the purpose of electrifying the south end of the Bala Sub (Richmond Hill line) may be to create a tail track to allow trains arriving Union from the west to unload and quickly leave the depot, running empty up to Rosedale siding before turning back. Pretty serious installation for that. That's in addition to the 3-train layover yard on the former CP line. There is no mention of retaining through running capability on the CP line for HFR or GO service.

- Paul

 

[Voltz]

I can't fathom how they will do this. It's only 739 feet from the bridge at St Clair to the point where the new duckunder track will have to enter a tunnel underneath the LSE line. That's a huge drop if that track crossing under the LSE is to meet the electrification plate dimensions. We will see if this holds up as they design it.

It's also a tight squeeze to build a 2-track tunnel north to Danforth Ave. Looks like they may lay a diversion track right on Midland while they do the construction. In all that's more tunnelling planned than Scarborough has seen since the SRT replacement debate began.

- Paul

Yeah that is steep,

I can see them shutting the line down south of Kennedy for a while and telling everyone to take the subway. and there is no way to divert the trains to the Richmond Hill line.

The walls of the new trench could be built on either side of the existing track while the trains are still running, but then it would have to be shut down while it is excavated.

Although I suppose a trench wide enough for one track could be built to one side, then run the trains though there while other half of it dug out.

 

[Allandale25]

There is no mention of retaining through running capability on the CP line for HFR or GO service.

- Paul

Good question for the open house. There's one at Evergreen. Or they could be emailed:

 

[mdrejhon]

That’s pretty steep to sink a track to a rail underpass in a mere 739 feet. It doesn’t make sense, but:

Speculation: Is this theoretically an electrified-train-only underpass? EMUs can handle steeper grades, but how steep? Stoufville Line is masterplanned to become ultimately an EMU-only route. That’s a potential clue.

 

[Allandale25]

^ Maybe it indicates the type of rolling stock that'll be used in the Initial Business Case for the Bowmanville Extension?

http://www.metrolinx.com/en/docs/pdf/board_agenda/20200220/20200220_BoardMtg_Bowmanville_Initial_Business_Case.pdf

 

[Kitsune]

Yeah that is steep,

I can see them shutting the line down south of Kennedy for a while and telling everyone to take the subway. and there is no way to divert the trains to the Richmond Hill line.

The walls of the new trench could be built on either side of the existing track while the trains are still running, but then it would have to be shut down while it is excavated.

Although I suppose a trench wide enough for one track could be built to one side, then run the trains though there while other half of it dug out.

There is a rail spur that is used by 3 to 4 business - and 2 are of the type that product cant really be shipped by truck. I guess it depends where the grade starts to go down.

It needs 7m clearance based off the Havendale pedestrian bridge proposed (which will close Havendale crossing and tear down 2 houses). That would make the grade 3.1% which from my understanding is ok for Passenger Trains. Won't see any freight trains ever use it. Which then leads us back to that rail spur - if it stays that is going to be a switching nightmare maybe. It does make me wonder how trains are currently shuffled to it.

 

[Northern Light]

There is a rail spur that is used by 3 to 4 business - and 2 are of the type that product cant really be shipped by truck. I guess it depends where the grade starts to go down.

It needs 7m clearance based off the Havendale pedestrian bridge proposed (which will close Havendale crossing and tear down 2 houses). That would make the grade 3.1% which from my understanding is ok for Passenger Trains. Won't see any freight trains ever use it. Which then leads us back to that rail spur - if it stays that is going to be a switching nightmare maybe. It does make me wonder how trains are currently shuffled to it.

GO's current maximum grade anywhere on the network is 2%. The Bomanville project had a grade issue noted, where if it were not correctable, it would limit diesel-hauled to 6 or 8 car consists.

Now, if you're EMU, they may well have more flex.

But that won't apply if freights need to use that section of track.

 

[CapitalSeven]

Grade issue - this may be a very naïve question, but the underpass is going to be practically used northwest-bound only. Is a steeper grade permissible for a "down" track than an "up" track?

 

[crs1026]

Grade issue - this may be a very naïve question, but the underpass is going to be practically used northwest-bound only. Is a steeper grade permissible for a "down" track than an "up" track?

Not naive at all, and I wondered myself if this might be the plan. Because ML.

In theory that’s possible, yes, but it is highly undesirable because a) leaves no flexibility if the other tracks is out of service for some reason and b) there’s always the chance that a train might have to back up and c) it does push the train’s braking effectiveness to the limit, with possible wheel skids when braking hard. That damages the wheels.

- Paul

 

[weekend_guy]

The walls of the new trench could be built on either side of the existing track while the trains are still running, but then it would have to be shut down while it is excavated.

Although I suppose a trench wide enough for one track could be built to one side, then run the trains though there while other half of it dug out.

Yep, that’s how it will be done. Likely shift the track as far west as possible without reducing the track speed below what is operationally acceptable, then a centre shoring wall with the east trench dug first. Memories of the West Toronto Diamond staging...

 

[Kitsune]

this picture I posted before shows there will be a diversion track:

and the unpreffered tunnel option provides an even better view of the diversion track:

compare this to the half the length havendale ped bridge:

It does make me wonder if they will ask the community if they can go a couple years without the corvette crossing to build a cheaper bridge.

Also regarding havendale.. yes tearing down 3 houses, chopping the front yard off a couple houses and check out that one house that is slated to have a couple inches between it and the cul de sac:

and all this to build one pedestrian overpass that I'm guessing is to facilitate access to the park:

it does make me wonder if it'll get deferred into infinity.

 

[mdrejhon]

Not naive at all, and I wondered myself if this might be the plan. Because ML.

In theory that’s possible, yes, but it is highly undesirable because a) leaves no flexibility if the other tracks is out of service for some reason and b) there’s always the chance that a train might have to back up and c) it does push the train’s braking effectiveness to the limit, with possible wheel skids when braking hard. That damages the wheels.

Triangle calculator gives 729 feet and 2 degree slope gives you 25 feet vertical elevation.

That's enough for a truss rail overpass with room for OCS underneath. GO electrification minimum clearance is 5946mm (19.5 feet) if you custom build it with the right materials, plate, etc.

(source)

25feet can be doable with 19.5 feet clearance + 5.5 feet rail deck underneath trussed bridge or (set of) bucket decks.

Tolerances are tight but should be doable without violating Metrolinx slope specs, and I've seen railroad truss bridges thinner than 5.5 feet from bottom-to-rails by using a slim railroad deck and a truss to stiffen a thin rail deck bridge. If you've driven east of Toronto on 401 through Pickering, you will often see this weird combination of 3 different rail bridge deck thicknesses:

-- Traditional I-deck at left
-- Truss bridge in middle
-- Bucket deck at right

(source -- http://beachburg.blogspot.com/2015/01/railway-bridges-of-ontario.html )

Theoretically, how frequently will a train need to do braking in that section? GO trains do have particularly effective brakes as we already know how it just decelerates nicely to a stop from 70-80kph to 0kph in the mere length of a platform, and doing so reliably without creating flat spots on the wheels.

As you can see, 729 feet with 2 degrees or (less) is no problem keeping within Metrolinx specs.

You just need to build a thin railroad deck and call it a day, and then you've got plenty of underpass room for OCS-height capable of supporting locomotive Bombardier BiLevels in both directions.

The good news is that you only need to build an underpass for a single track -- not a giant 4 track corridor -- a very short air hop. So should be easy to keep the rail deck thin, even just simple I-beams. But you could also try to decrease the slope to ~1.8 degrees, and use an even thinner bridge; or use it to zero the gradient at the curve before the 729 feet. The tricky part is building the bridge without distrupting service...

 

[crs1026]

Still, 729 feet gives you about 30 feet vertical elevation for 2 degrees slope with a quick napkin math.

That's enough for a slim rail overpass with room for OCS underneath. If you have to, you can simply truss the rail overpass to have more OCS room underneath.

Tolerances are tight but should be doable without violating Metrolinx slope specs.

Theoretically, how frequently will a train need to do braking in that section? GO trains do have particularly effective brakes as we already know how it just decelerates nicely to a stop from 70-80kph to 0kph in the mere length of a platform, and doing so reliably without creating flat spots on the wheels.

That’s some napkin.... two percent at seven hundred feet is 14 feet in elevation. Three percent is 21 feet. ML’s preferred vertical clearance for electrification is 7.584m or 24.9 feet. The overhead beam structure will need a couple feet of depth. Railhead to railhead, we are talking 27 feet or more.

Passenger equipment has ABS-like equipment to protect against wheel sliding - the technical term is ‘decelerometer’. The tradeoff, as with automotive ABS, is a longer braking distance.

Assuming that a GO train dropping into the tunnel has just left the Kingston main line through a standard 45 mph turnout, there is little fear of a “runaway” train, especially if there is an upgrade from the underpass under Danforth. But it would be quite the ride, and it’s well outside GO’s normal parameters. I’m not in favour of building new to tolerances that will constrain things.

- Paul