Updated January 22, 2017: Additional illustrations.
The TTC begins its 2017 round of subway shutdowns on the weekend of January 21-22 with the complete closure of the Spadina line north from St. George Station. This is the first of a series of monthly weekend tests of the new Automatic Train Control (ATC) system leading to a planned conversion from Dupont north to Wilson in the fall. This is a prelude to opening the Spadina extension, which has only ATC, not “conventional” signals, to Vaughan at the end of 2017. Most of the closures are on Line 1 YUS because this testing is on top of shutdowns for routine maintenance work.
Two three-day weekends, Easter and Thanksgiving, will see Line 2 BD shut down for work on the Prince Edward Viaduct.
There are important changes for 2017 in plans for shuttle bus operations.
For the Spadina shutdowns, the TTC will not attempt to operate a parallel bus service over the entire route as it is plagued by construction at some locations, and generally provides a long trip south to St. George Station. Instead, bus service will be improved on east-west routes to get people over to Yonge where they can make the trip downtown quickly on the subway. A “parallel” bus service will operate only on the north end of the Spadina line between Downsview and Lawrence West Stations.
In past years, the scope of some shutdowns has been wider than the subway track layout and the locations of turnbacks would imply. The reason for this is that the power feeds to many potential turnbacks are not designed to support operations when power is available on only one side of the location. An example of how this was fixed is at Bloor crossover.
At Bloor, the power feeds are segmented into separate pieces:
- Southward from the south end of the station
- Bloor Station and crossover, plus the track to roughly halfway to Rosedale Station, one train length north of the crossover
- Northward from the midpoint between the crossover and Rosedale Station
This allows trains to terminate at Bloor in either direction even if the power is off south to Wellesley or north to Rosedale. When the line was designed, the crossover itself was the gap between two power sections, and so this could not be a turnback point if power was cut on either side. This change, including the resignalling of the crossover, was installed as part of the North Yonge subway project.
Power supplies at crossovers at Rosehill (south of St. Clair), College and King have not yet been modified, but this is in the plans as part of the ATC project on the Yonge line. The new signal system will include the ability to manage these crossovers remotely as is done at Bloor.
A similar problem exists at some of the older turnbacks on the BD line. Whenever work is underway on the Viaduct, subway service has ended at Pape (although it physically operates west to Chester centre track) because power cannot be cut on the Viaduct without also cutting it at Broadview Station. The TTC will be installing a gap in the power feed just west of Broadview Station so that trains can use this as their terminal. Shuttle buses on Danforth will not be required (only from Broadview westward), and subway riders will have access to the downtown streetcar lines as an alternate route to the core on Dundas and King.
A planned shutdown at Union would normally have required shuttles south on Yonge below Bloor, but subway service will be operated using the crossover at King. This will be done on a manual basis because the new signals and controls for the crossover are not yet in place. This tactic will also be used in 2018 when work at Davisville would have required a shutdown north of Bloor. Instead, the crossover at Rose Hill will be manually operated so that shuttle buses can make their connection at St. Clair Station where there is an off-street loop.
Shuttle bus operations have gradually improved, notably by actively changing the traffic environment in which the buses must operate rather than simply hoping for the best as the streets were. Parking restrictions, signal changes and the use of Paid Duty Officers were much needed changes, although one must wonder why it took the chaos of previous years’ events to show that replacing the subway with buses required a lot of accommodation by users of the streets.
Many types of work were undertaken during the shutdowns beyond the most obvious track and signal upgrades. These are described in the presentation to the TTC’s Board on January 18. Of particular interest was one project that is not illustrated in the report, the replacement of 900m of subway track on the western part of Line 2 with a new form of rail support.
All subway lines built before the Spadina line opened have the track mounted directly on the concrete tunnel floor with only a rubber pad that doubles for both vibration and electrical insulation. Spadina saw a shift to the “floating slab” technique where the rail is mounted to large concrete sections that in turn sit on large rubber pads. This structure requires a deeper tunnel, but it provides better vibration isolation. Older lines cannot be retrofitted because adding a new layer of support would make trains too high for the tunnels.
The TTC has installed an experimental section of track where the rail is supported from the side rather than from below with rubber pads gripping the track below the head of the rail. The result is a roughly 20db reduction in vibration. This is a trial, and there are currently no plans or funding to retrofit other problem sections of the subway.
The new track suspension system is described on the vendor (Pandrol) website, and illustrated below in photos provided by the TTC.
Updated January 21, 2017
The following illustrations are from a presentation provided by the TTC. The first gives the rationale for use of the Panguard track mounting system and includes a good cross-section of the track suspension technique.
The following diagrams show before (yellow) and after (blue) vibration measurements.