Another interesting tidbit I found regards what Ontario officially calls "split phasing", they call it "separate phasing". But the manual shows that during the yellow phase, the yellow ball and yellow arrow must be displayed together, in fact I can only think of 2 intersections that currently do this, and it's a rather recent installation too. Consider this document is from 2001. This is on Page 41
I'm confused here. I thought split phasing would always require the yellow ball and arrow to be displayed together. Would you mind explaining how this wouldn't be the case? For example, you mentioned the Bovaird Dr/Mountainash Rd intersection in a different thread, which is split phasing. Does this have the yellow ball and arrow together?
In most places that use split phasing or separate phasing....since most posters here are familiar with the FHWA jargon, I suggest that we use that terminology preferably.
http://ops.fhwa.dot.gov/publications/fhwahop08024/chapter4.htmIncidentally, they use an example FROM Toronto here in Section 4.3.5.
As for the split phasing, I got off on a bit of tangent to start off here, in nearly ALL cases in the GTA in which I have seen split phasing used. Like at Mountainash/Bovaird/Sunnyvale. The green phase shows a green ball + green arrow, but when the light turns yellow, the green arrow disappears and just a yellow ball appears. Although at Airport/Intermodal/Woodslea, the yellow arrow has been showing recently with the yellow ball on ONLY the Intermodal split phase (The Woodslea split phase does not display the yellow arrow). So most split phases in Ontario follow this sequence in reality:
Red Ball
Green Ball + Green Arrow
Yellow Ball
Red Ball
Lagging left turns in a permissive-protected situation are known as "extended greens", it makes sense as this is an opposite of the advanced green, indeed I always the "advanced" in advanced green referred to it being a super duper green light (if you get what I mean) but it refers to it being advanced, as before the through traffic signal.
Extended Greens can ONLY be used in situations in which opposing traffic CAN'T TURN LEFT. Of course this eliminates the yellow trap, which is illegal to run in Ontario. All this shown on Page 40.
Incidentally, they refer to a lagging left in a fully protected situation as "lagging" and not extended....meh, no need to complicate matters do we.
I don't think I've ever seen an extended green in Ontario. It would have to be used from a two-way street to a one-way street. I personally think the Regina St/Bridgeport Rd and Regina St/Erb St intersections could use these at peak times. Currently, there is an advanced green, but I think both an advanced green and an extended green could be useful at rush hour, since a single vehicle trying to turn left is enough to block everyone behind them.
I still can't believe the yellow trap exists; thank God it's not found in Ontario 
An extended green or lagging left probably does exist somewhere in Ontario, but it would most likely be found at a T intersection.
It could in theory be used at a regular intersection where 2 two way streets intersect, the yellow trap is prevented when the side opposing the direction that gets the lagging left has a left turn restriction. Take for example Dundas St and Bay St, NB Bay has no restriction at all on left turns while SB Bay has a time restriction, I believe 7AM-7PM on weekdays (You learn the time restrictions fairly quickly when you Uber downtown for a few weeks)
Since SB Bay can't make a left turn (at least during this time restriction), then there is no issue with running a lagging left (or extended green) on NB Bay as there can't possibly be a yellow trap situation.
At the intersection of Yonge and Harbour, if you are turning left onto Yonge, the green arrow signal appears later on in the phase, but this lagging arrow appears moreso as a protection against pedestrians than oncoming traffic. This intersection is strange and I have not observed the phasing here like I have at many other intersections, so I am not 100% sure of what goes on here. But I know as a fact that the green arrow appears long after the green ball has been on.
As for a lead and lag for the same left movement, it sounds like an interesting proposition, I wonder if that is done anywhere currently. Understand that if you have both a lead and lag movement for the same left turn movement, that the opposing direction will face more red time, as will the cross traffic on the one way street. It appears that there is not enough space for two actual lanes in this situation. So just looking at this situation, how about redesigning the intersection, I'm not sure how active this intersection is with pedestrians, but what if we have an actual left turn lane and a through lane on one side, and an option lane on the other side (straight or right), if pedestrian activity is high at this intersection, the option lane would not be feasible. (If pedestrian traffic is low enough, the pedestrian crossing that can create the conflict could be removed, I know this is not ideal, but it can be done)
As for a FULLY PROTECTED lagging left, I know they exist at Lake Shore/Windermere, and Lake Shore/Colborne Lodge. What happens here, Lake Shore Blvd gets a green ball for EB and WB, the light for WB Lake Shore changes back to red, and then the EB Lake Shore Blvd LEFT TURN signal displays the green arrow. This is an intersection that clearly shows the positives of the FYA, as this is a single left turning lane, if traffic is clear on opposing Lake Shore, one could make the turn during a flashing yellow arrow, as in the current setup would be a solid red throughout the whole phase until their green arrow appears for the left turn.
30-20-20 was definitely the most common install in Southern Ontario until relatively recently and still by far the most common in many areas, including the Niagara Peninsula. The flashing green ball was basically the Ontario version of a 4-section with a green left arrow.
All new signals to my knowledge are still the 30-20-20 variety normally.
The flashing green ball may have been our version of the doghouse but not exactly. The flashing green ball only allows for one type of phase unlike the many others the 4-section does, the flashing green ball can't mimic the "red ball + green left arrow" movement, it's impossible.
Of course, with the flashing green ball, you have absolutely NO IDEA when the phase will end, generally as I recall seeing these more common in my real younger days, like early to mid 90s, when the flashing green ball became solid, opposing traffic instantly got a green, there was no clearance phase involved.
Sometime in the late 80s, the advanced green defined by the green ball + green arrow appeared in the manual, and seeing as there are some kicking around today, that means it has taken nearly 30 years to make the flashing green ball extinct. I know the FYA is supposed to do the same thing across every state, we might still be seeing doghouses 30 years from now.