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Leaside Bridge

dunkalunk

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Just putting this out there to see if anyone knows the answer.

Could the Leaside Bridge (the one that carries Milwood Drive across the Don) carry rail transit? From photos it appears that there is a hollow box truss below the road deck that looks similar to the one of the Prince Edward Viaduct which carries the Bloor-Danforth Subway.
 

DSC

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Just putting this out there to see if anyone knows the answer.

Could the Leaside Bridge (the one that carries Milwood Drive across the Don) carry rail transit? From photos it appears that there is a hollow box truss below the road deck that looks similar to the one of the Prince Edward Viaduct which carries the Bloor-Danforth Subway.
It was apparently built to support a streetcar BUT when it was widened a few years ago this additional weight means it no longer can. In 2010, when Transit City was being discussed, Steve Munro wrote "This bridge was originally only four lanes wide with extra structural support for a streetcar extension north from Pape and Danforth. That support was substantially consumed by the bridge widening to six lanes. The TTC is looking at a special lightweight trackbed as a means of staying within the bridge’s capabilities. "
 

dowlingm

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I live in the general area and drive or take the 56 bus across the bridge at least weekly. Looks to me like the subway will need a new crossing of the valley now that the complete insanity of a surface LRT along Pape has been quietly deprecated. Most direct would be up Pape and continuing under Minton Place with a span curving around to Overlea and Millwood, setting up for a continuation along Overlea towards Don Mills with maximum penetration of Thorncliffe Park with minimum need to traverse foundations. I have no doubt the folks who own property at the Minton end won't love that but there are few ways to cross the valley in that area and not disrupt a leafy enclave.

In some ways I think the "how to get from Thorncliffe Pk Dr/Overlea to Don Mills" curve might be trickier.
 

Hipster Duck

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Let's say we build the DRL as a subway as far as Don Mills and Eglinton. Given the need to build a viaduct anyway (unless the TTC wants to build some kind of elaborate spiral tunnel on either side of the ravine), would it make sense to build a replacement for the Leaside bridge that incorporates both the subway and a new road?
 

nfitz

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Let's say we build the DRL as a subway as far as Don Mills and Eglinton. Given the need to build a viaduct anyway (unless the TTC wants to build some kind of elaborate spiral tunnel on either side of the ravine), would it make sense to build a replacement for the Leaside bridge that incorporates both the subway and a new road?
Probably not given a) that the Leaside Bridge was recently completely rehabilitated.
 

dunkalunk

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In my concepts, I have placed the subway on it's own bridge directly south of the Overlea bridge. Placing it on the south side also allows for a gentler curve between Marc Garneau C.I. and Valley Park Middle School to meet Don Mills Road.
 

BurlOak

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No, it can't. It was built to accommodate a streetcar route (which never arrived) on its road deck, but the extra strength required for that was used up when the bridge was widened in the 1960s. As recently as five years ago, the TTC wasn't certain that the Don Mills LRT could be safely incorporated onto the bridge using their track construction methodology.

The box truss isn't large enough for a two-track subway (or a double-stacked one-track subway).

http://en.wikipedia.org/wiki/Leaside_Bridge
Is it possible (based on geometry) to put in a two-track Sky Train between the trusses. Strengthening a truss bridge is not that difficult, assuming that the foundation and piers are adequate. Although it may be a bit risky attaching a new transit line to an 85 year old bridge.

PS. it is a bit embarassing that the bridge took 10 months to build in 1927. Now it would take about 3 years.
 

diminutive

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PS. it is a bit embarassing that the bridge took 10 months to build in 1927. Now it would take about 3 years.
Construction would take 3 years, the EA process 5.

Just building a two track span across the Don Valley really shouldn't be very expensive at all. Well under the per-km average costs the TTC estimates for the TTC.
 
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dowlingm

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Given the paucity of valley crossings (only Pottery Road, Millwood, Don Mills and then Woodbine) any messing around with Leaside Bridge which would involve full closures would probably be a tough sell to put it at its most kind. As it stands the queue to access Don Mills can stretch quite a ways in both directions on O'Connor. Once you got across the bridge you wouldn't have as good an angle to turn for Overlea.

The only upside would be that the train deck would be sheltered by the road deck. You could put a deck over the subway bridge but that would only make sense if you wanted to redirect Pape and simplify the tricky triangle junction at the south end to be primarily to Donlands with the other access becoming a sideroad. Given the capacity of the refurbed LB and the residential zone on Minton again that seems like a needless fight to pick.

dunkalunk - that seems like a tight turn for a subway to make with little room to jog south due to Marc Garneau. Basically for me if it's tighter than King-Union, it's probably too tricky to attempt.
 

BurlOak

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Given the paucity of valley crossings (only Pottery Road, Millwood, Don Mills and then Woodbine) any messing around with Leaside Bridge which would involve full closures would probably be a tough sell to put it at its most kind. As it stands the queue to access Don Mills can stretch quite a ways in both directions on O'Connor. Once you got across the bridge you wouldn't have as good an angle to turn for Overlea.

The only upside would be that the train deck would be sheltered by the road deck. You could put a deck over the subway bridge but that would only make sense if you wanted to redirect Pape and simplify the tricky triangle junction at the south end to be primarily to Donlands with the other access becoming a sideroad. Given the capacity of the refurbed LB and the residential zone on Minton again that seems like a needless fight to pick.

dunkalunk - that seems like a tight turn for a subway to make with little room to jog south due to Marc Garneau. Basically for me if it's tighter than King-Union, it's probably too tricky to attempt.
What exactly is the radius at King-Union? I thought I have seen a minimum acceptable radius is 300m, but I believe this one is less. I also thought I have seen a number of about 120m as well, but maybe that was the minimum for yards.
 

innsertnamehere

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I would almost want a new transit only bridge built. Make it a cable stayed bridge, it could become a new icon for the city when driving down the DVP. (Or taking the new DRL, of course)
 

BurlOak

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I would almost want a new transit only bridge built. Make it a cable stayed bridge, it could become a new icon for the city when driving down the DVP. (Or taking the new DRL, of course)
I like cable stayed bridges as much as the next guy, but I think it would be a great story if rapid transit could be placed under the bridge 85 years after construction. Part of Toronto's history is that the Prince Edward (Bloor) Viaduct recieved the subway 5o years after construction. This would beat it by 35 years.

Instead of subway (HRT), maybe SkyTrain vehicles are lighter and can more easily be accomodated on the bridge to reduce the strengthening required. They may also be able to make the tigher curves to get under the bridge.
 

junctionist

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An architecturally impressive bridge would be great and appropriate in crossing the grandest ravine of a city of ravines. The Don Valley is quite scenic in the area of the Leaside Bridge with a landscape of rolling greenery when one looks towards downtown. Surprisingly, it reminds me of some of the urban landscapes around Pittsburgh, which is in a US state known for its topography (Pennsylvania). A great bridge would bring more attention to the area. The Leaside Bridge may be historic, but if you see the Bloor Street Viaduct first on the DVP, it looks rather "no frills".
 

dowlingm

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I like cable stayed bridges as much as the next guy, but I think it would be a great story if rapid transit could be placed under the bridge 85 years after construction. Part of Toronto's history is that the Prince Edward (Bloor) Viaduct recieved the subway 5o years after construction. This would beat it by 35 years.
The reason that is history is because the capability (more or less - the original plan was streetcars) was designed in. Introducing sharp curves (and the associated noise) just to make a point seems imprudent as opposed to a new bridge with a gentler curve, especially as retrofitting the bridge would hardly be cost-free since the bridge would either have to be closed or extreme caution taken while traffic passed overhead during any structural works.

Also, reintroducing ICTS just as we got rid of it with the SRT closure also seems unwise - Steve Munro estimates the capacity of the line to be 4 subway-car length which would probably push an ICTS to 6 car length on day one with no fleet economies of scale to take advantage of either from the conventional light rail or heavy subway direction.
 

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