Glad to hear that that intersection is still working well. I've stood there and it's really satisfying to see the white light turn on exactly when the streetcar arrives, stay on for a few seconds, then the signal goes back to its normal program. I can't share the details of the signal programming, but I can point you toward some things which are publicly visible, which may help answer some of your questions.
Streetcars are tracked using in-road detectors, and the signal timing is adjusted in an attempt to line the transit phase up with the streetcar's arrival. You can recognize streetcar detectors from the black rubber rectangle over them (though the blackness fades over time). Here are the streetcars detectors you can see at St Clair & Gunns via Streetview:
Westbound departing Keele St stop (200 m before stop line)
View attachment 431913
Westbound approaching Gunns (100 m before stop line) - this one's pretty hard to see
View attachment 431915
Westbound approaching Gunns (80 m before stop line)
View attachment 431914
Westbound at Gunns (just past stop line)
View attachment 431916
Eastbound approaching Gunns, just after crossing WB lanes at a stop sign (40 m before stop line)
View attachment 431917
Eastbound at Gunns just past the stop line
View attachment 431918
Some factors you should consider when figuring out why a streetcar got stopped at a red light:
- How early can the signal get an accurate estimate of the streetcar's arrival time? The further away the streetcar requests priority, the more time the signal has to do things like end conflicting phases or extend the light if it's already green. However, the further away the request is, the less accurate the estimated arrival time will be for the streetcar. Inaccurate estimated arrival times can have a huge negative impact on the effectiveness of priority, to the point that the priority intervention could actually delay the streetcar even more than if there hadn't been any priority request. Depending on the priority setup and the road layout leading up to the intersection, it may be possible to use additional detectors to update the arrival time estimate as the streetcar approaches. This is not very common, but as you saw above, WB at Gunns is one such example. The best case scenario is a long uninterrupted run from the previous stop/signal (like WB at Gunns or WB at King & John). The worst case scenario is a near-side stop: then you have no accurate estimate of when the streetcar will wish to proceed until it's too late.
- What was the signal doing when the streetcar requested priority (e.g. when it left the previous signal/stop)? Was there a long pedestrian crossing active which couldn't count down in time? At St Clair and Gunns, the north-south crosswalk is 25 m long, so based on a
walking speed of 1.2 m/s, the Flashing Don't Walk should be 21 seconds. Then figure another 7 seconds for yellow and red, and it takes 28 seconds to end the north-south phase. For comparison, the 200m westbound zone at Gunns would translate to a travel time of around 20 seconds at 10 m/s (36 km/h).
- Which direction is the streetcar going (EB or WB)? Is there also a streetcar going the opposite way? The priority parameters are often different in one direction than another, especially at intersections such as Gunns Loop where one direction is going straight while the other is turning.
- How long was it since the previous streetcar? Some intersections have conditional priority which provide higher levels of priority to streetcars which have an above-average headway in order to even out the service.
Completely agree ... except transit priority is known as "TSP" (Transit Signal Priority) in North America. Not sure why they chose that term, but that's what you need to search if you want to learn more about it. TPS stands for Toronto Police Service.
Also, it's neither practical nor necessary for every route to have a ROW. You can achieve the same result in other ways such as by setting up modal filters which make it impossible to use the streetcar route as a through route. Similar to the King pilot.
Exactly. This is known as "phase insertion". If a left turn phase is about to turn green but there's a streetcar approaching/waiting, a short transit phase is inserted into the cycle, then once the streetcar has cleared the signal picks up where it left off in the cycle (left turn phase). On streets with signal coordination (most streets in Toronto), some other phases will need to be shortened to make up for the time used by the inserted streetcar phase. It's fairly common in Toronto for turning streetcars but fairly uncommon for streetcars going straight.
In this old video of mine (from Feb 2019) I provide the basic background for how the Toronto's priority system works:
