Single-lane left turns converted from protected-permissive to protected only

[jakeroot]

There is also some advantage in being able to implement delayed left turns to improve coordination along some corridors (which you don't get with opposing protected-permissive signals, which are leading-only (or lagging-only like here in Japan)). What will worry me is if we start to see protected lefts pop up along roads with only one lane in each direction, you see that in WA/OR/CA (especially CA), it can be very irritating.

You don't have to use leading protected lefts for opposing protected-permitted left turn signals–with an FYA, you can use lead-lead, lag-lag, or lead-lag. It just seems that a lot of practitioners will default to lead-lead.

Absolutely, totally agree. But unfortunately, the FYA is not an official traffic control device in Canada.

Edit: the beginning of that paragraph does provide some important context:

The intersections that have been modified in Surrey all seem to be situations where they are (as you mention) fairly major intersections, and I can kind of see what they are going for switching these to protected lefts. There is also some advantage...

[bcroadguy]

Surrey, BC has been doing this a lot lately. They converted at least 11 protected-permissive left turns to protected only as part of their Vision Zero program. I'm sure they have converted even more since this page was last updated in 2020. All of these are pretty major intersections.
https://www.surrey.ca/services-payments/parking-streets-transportation/vision-zero-surrey/fully-protected-left-turns

Other cities around here don't seem to be doing this much. I can't think of any examples around here other than this one on 200 Street in neighbouring Langley: https://www.google.com/maps/@49.1708579,-122.6681214,3a,75y,161.02h,91.57t/data=!3m6!1e1!3m4!1s7-1nhSO7GulLgDuVlF2LLw!2e0!7i13312!8i6656?entry=ttu and a few along North Road in Burnaby / Coquitlam when the SkyTrain was added to the median, reducing visibility.

I've always associated BC (and Canada in general) with permissive left turns, at least for single-lane left turns. Never really felt like protected lefts were overused, they always seem relegated to situations where they also seem warranted (lots of oncoming lanes, high speeds, poor visibility, overlapping with oncoming left turn lane, etc). Compared to other west coast regions (WA, OR, CA) where protected lefts are highly overused, BC is kind of a breath of fresh air.

The intersections that have been modified in Surrey all seem to be situations where they are (as you mention) fairly major intersections, and I can kind of see what they are going for switching these to protected lefts. There is also some advantage in being able to implement delayed left turns to improve coordination along some corridors (which you don't get with opposing protected-permissive signals, which are leading-only (or lagging-only like here in Japan)). What will worry me is if we start to see protected lefts pop up along roads with only one lane in each direction, you see that in WA/OR/CA (especially CA), it can be very irritating.

I have noticed the new intersection at Mountain Hwy / Keith Road is fully protected, despite only one of the approaches being a double left turn. I know this signal isn't "new" at this point, strictly speaking anyways, but I remember when it popped up that I was surprised to see every approach being protected-only. But other signals in the project area are not all protected-only, like the left onto westbound Hwy 1 (weird right-side left turn signal there too).

All of Mountain Highway / Keith Road's left turn signals being protected is definitely unusual. I don't think there is a trend of protected-only left turns along two-lane roads in BC.

That right-side left turn signal is very weird. I've seen similar signals when there is a left turn lane and a left/straight lane (example), but only in that situation.

[fwydriver405]

Just passed by what used to be a fully permissive left (circular green), now removed with a fully protected one in Waterville yesterday at Route 104 at I-95 NB ramps, as part of the Build Grant signal replacments.

Got to get a picture of the phasing change as shown here on Route 104:


Also discovered an additional intersection in Winslow that got the reverse treatment from fully protected to pm+pt phasing, with a shared signal for now. Not sure if this means an FYA conversion here or if they are testing permissive operation here, because the original Build Grant plans called for keeping the fully protected phasing on 3 out of the 4 approaches. Before, at Carter Memorial Drive at Route 201, and now the interim phasing:


For intersections that are being converted to FYA in Waterville, it looks like they are installing the new heads first with shared indications with the existing TS2 controller, and then they change it over to FYA once the new ATC controller is up and running.

[fwydriver405]

A few signals on Massachusetts Ave in Boston were converted from double-lagging PPLT (YoG) to double-lagging fully protected lefts between Columbus Ave and Albany St. These were taken a little over 60 days apart at Columbus Ave - the PPLT photo was taken on 27 July 2023, and the fully protected photo on 26 September 2023. The phasing is exactly the same, minus the permissive phase for the left turning traffic.

[RobbieL2415]

That should be safer for pedestrians and cyclists.

[andrepoiy]

This intersection converted to protected.

I suspect the reason is that they noticed higher collision rates. Given that the roadway speed limit is 80 km/h and drivers usually go 100 km/h here, and that population growth has resulted in higher AADT over the years, they decided to go for protected.

I have noticed that because it is now protected, the left turn arrow turns on for a lot longer and increases delay for opposing traffic.

Before:


After:



Link:https://maps.app.goo.gl/A16kpcuVwuY3xKWn8

[mrsman]

Protected only seems justified given the high speeds in this corridor.

[fwydriver405]

That should be safer for pedestrians and cyclists.

I agree on that part, however I kind of feel like they should have it so that the thrus and the lefts can gap out at different intervals once the pedestrian phases are complete, now that the risk of yellow trap is eliminated by removing the permissive left turns. There are loops in the ground at Mass at Columbus Ave, though not sure if they are used for something else and/or for traffic monitoring as most Boston signals are pretimed.

[fwydriver405]

Build Grant signal conversions are breaking ground in Sanford currently, which does include the removal of permissive phases at two intersections on Main St, at Westview Dr and at the Shaws Plaza (only Westview has been converted so far), due to the left turn crossing two thru lanes. Right now the new signals at Westview are still on the old controller with the existing timings, with the reservice yellow trap on Main St removed.

March 17, 2023


April 13, 2024