How would priority ideally be set up at major intersection given that they also have streetcars running perpendicular to Spadina that should not get delayed? I assume there is a solution but it's not immediately obvious.
The simplest method to introduce signal priority at major intersections along Spadina while minimizing impacts to east-west streetcars would be to introduce north-south green extensions and compensation-based offset correction.
Compensation-based Offset Correction
The signals along Spadina are coordinated, so they need to maintain a constant average cycle length to stay in sync with each other. So if you add 10 seconds to one cycle, you need to remove 10 seconds from the next cycle(s) to bring the signal back into sync (known as offset correction). To avoid reducing green time for east-west traffic (including mixed-traffic streetcars), the offset correction can be set up to compensate other movements for the timing change caused by the streetcar. For example, if the signal gave 10 seconds of extra green to a Spadina streetcar, the next cycle(s) it would reduce the green time for Spadina by 10 seconds to provide a higher percentage of green time for the east-west road and left turns. Compensation-based offset correction is already used at a couple intersections in Toronto.
The limitation to offset correction is that there's only so much time you can reduce from a given phase. Here's my guess at the signal timings based on the
City's operational policies, assuming a cycle length of 90 seconds and a walking speed of 1.2 m/s.
It is possible to reduce the North-South green by 14 seconds, so it's possible to recover 28 seconds over the course of two cycles after the streetcar leaves without taking any time from the phases that were delayed by the green extension. 29 or 30-second extensions would require 3 cycles to recover, but such long extensions would be rare given the detection zones I'll be proposing. Over the course of the TSP action and subsequent offset correction, all phases would have received the same total green time as they would have in the absence of a TSP call.
Type of Green Extension
The biggest challenge for signal priority at major intersections along Spadina is that they have track switches limiting streetcars to 10 km/h. The distance to clear is about 30 metres, and streetcars are 30 metres long. So at 10 km/h (2.8 m/s), it takes 21 seconds for the streetcar to clear the intersection. So streetcars need to enter the intersection before the start of FDW to have enough time to clear. Many operators already know this and don't enter the intersection after the FDW has begun.
Spadina & Dundas:
The green extension therefore needs to be provided as Green & Walk. Ideally the transit signal would be adjusted to change to red at the last moment streetcars can practically enter the intersection, to provide a more accurate indication to operators whether they still have enough time to cross the intersection. Since the start of FDW and the start of streetcar amber would be at about the same time, the maximum practical extension depends on how far in advance the streetcar's arrival can accurately be predicted.
Southbound towards Dundas, it's 163 metres from the previous signal at St Andrew St. That provides about 19 seconds of reliable advance notice, which is pretty much perfect for a 30-second extension: it provides a 11-second buffer in case the streetcar travels slower than expected.
Northbound towards Dundas, it's 168 metres from the far-side stop at Sullivan St, which provides about 20 seconds of reliable advance notice, which is also pretty much ideal for a 30-second extension. Both of these detection zones consist of a dedicated streetcar lane without any intermediate stops or intersections so it is very unlikely that a streetcar would ever miss a green extension that it requested.
Conclusion:
It appears possible to introduce up to 30 seconds of Green/Walk extension north-south at Dundas & Spadina, with relatively minor impacts on east-west streetcars. King & Spadina, Queen & Spadina and College & Spadina are similar and would also benefit from a similar setup.
