Traffic signal

[jakeroot]

Not exactly the most interesting thing out there, but unusual for *most of* WA.

In the work zone for the WA-18 / I-90 DDI construction, northbound Echo Glen Road (Snoqualmie Parkway) had its dedicated left turn lane removed, and thus the dedicated left turn signal (FYA) was also removed. Left turns are still permitted, but it's now an option lane with two through lanes.

To accommodate this change and to keep in line with the MUTCD, the left-most through signal was replaced with an inline-5 "yield on green" tower. These types of left turn signals are wicked common in the Midwest, but rare as hell in Washington (except for mast-mounted supplemental signals, and in Tacoma ("Tacoma Tower") where they are so common that I'm pretending they don't exist for the purposes of this post...)

Given the move away from both option-lane left turns, and shared left turn faces, I would have to assume this will be one the very last of these installed in WA, outside of this exact situation repeating itself in the future. And even then, I'm not entirely sure what stopped them from installing a doghouse instead. And even in Tacoma, the city only installs FYAs now.

For the record, I'm aware of a handful in Olympia and maybe a couple or two way up in Whatcom County, but by and large "yield on green" shared left turn signals are 5-section doghouses or 4-section bimodal signals in WA. Even in Spokane, the left-side supplemental left turn signal is usually a doghouse!

[Big John]

^^ Odd thing on the last link is that next to and 90 degrees from the doghouse is an inline 5-section signal with right turn arrows.

[roadfro]

Flashing green beacon for a ramp meter on the Los Feliz Blvd on-ramp to I-5 North in Los Angeles, CA - in this case, the leftmost lane is an HOV lane which does not stop, while the centre and rightmost lane are metered. Not sure if the green beacon still blinks or is solid to this day in operation.

Streetview
In operation, 10 Feb 2020

I kinda like this. I've always thought ramp meters being dark when not in metered operation isn't a good idea, and that flashing green could be a good way to indicate that metering isn't running.

... and a few pedestrian crossing signals as well, though most are being changed out for flashing yellow, PHBs, or other treatment.

Not as much of a fan of this when flashing yellow at intersections is a standard thing.

[Big John]

Flashing green beacon for a ramp meter on the Los Feliz Blvd on-ramp to I-5 North in Los Angeles, CA - in this case, the leftmost lane is an HOV lane which does not stop, while the centre and rightmost lane are metered. Not sure if the green beacon still blinks or is solid to this day in operation.

Streetview
In operation, 10 Feb 2020

I kinda like this. I've always thought ramp meters being dark when not in metered operation isn't a good idea, and that flashing green could be a good way to indicate that metering isn't running.

I like the Minnesota policy of flashing yellow when not in operation.

[jakeroot]

^^ Odd thing on the last link is that next to and 90 degrees from the doghouse is an inline 5-section signal with right turn arrows.

Yeah! Spokane is a weird place. That would be the norm for the right turn signals, as it is in other parts of WA, too (bimodal 4-section signals, too).

[roadfro]

Flashing green beacon for a ramp meter on the Los Feliz Blvd on-ramp to I-5 North in Los Angeles, CA - in this case, the leftmost lane is an HOV lane which does not stop, while the centre and rightmost lane are metered. Not sure if the green beacon still blinks or is solid to this day in operation.

Streetview
In operation, 10 Feb 2020

I kinda like this. I've always thought ramp meters being dark when not in metered operation isn't a good idea, and that flashing green could be a good way to indicate that metering isn't running.

I like the Minnesota policy of flashing yellow when not in operation.

Nevada uses two-section heads for ramp meters, so that's not an option here. But even in places I've been that use three-section heads, I've never seen that. Seems like a good idea.

Similarly, I don't like how HAWKs are dark until activated, but that's another topic...

[PColumbus73]

https://www.google.com/maps/@35.7433314,-78.762743,3a,15.5y,62.52h,92.77t/data=!3m8!1e1!3m6!1s0FSk6CFvqKNs1NrHEmPd_A!2e0!5s20241101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-2.771208232583689%26panoid%3D0FSk6CFvqKNs1NrHEmPd_A%26yaw%3D62.516048290899796!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIwNC4wIKXMDSoASAFQAw%3D%3D

As anyone seen part-time dual left turn lanes? The left turns don't go onto a road with a reversible lane, nor is one left turn lane an option lane, nor is it in front of a stadium or somewhere else that might experience a short-term surge.

[plain]

https://www.google.com/maps/@35.7433314,-78.762743,3a,15.5y,62.52h,92.77t/data=!3m8!1e1!3m6!1s0FSk6CFvqKNs1NrHEmPd_A!2e0!5s20241101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-2.771208232583689%26panoid%3D0FSk6CFvqKNs1NrHEmPd_A%26yaw%3D62.516048290899796!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIwNC4wIKXMDSoASAFQAw%3D%3D

As anyone seen part-time dual left turn lanes? The left turns don't go onto a road with a reversible lane, nor is one left turn lane an option lane, nor is it in front of a stadium or somewhere else that might experience a short-term surge.

Yeah I don't see the point of it at all. That is a very strange setup.

[fwydriver405]

https://www.google.com/maps/@35.7433314,-78.762743,3a,15.5y,62.52h,92.77t/data=!3m8!1e1!3m6!1s0FSk6CFvqKNs1NrHEmPd_A!2e0!5s20241101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-2.771208232583689%26panoid%3D0FSk6CFvqKNs1NrHEmPd_A%26yaw%3D62.516048290899796!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIwNC4wIKXMDSoASAFQAw%3D%3D

As anyone seen part-time dual left turn lanes? The left turns don't go onto a road with a reversible lane, nor is one left turn lane an option lane, nor is it in front of a stadium or somewhere else that might experience a short-term surge.

Yeah I don't see the point of it at all. That is a very strange setup.

Many states don't allow double left turns with permissive phasing -  this is done so they can run an FYA in fully protected mode with double left turn lanes for capacity during peak periods, and run it in permissive/protected with a single lane during off peak periods when traffic is lighter.

[freebrickproductions]

https://www.google.com/maps/@35.7433314,-78.762743,3a,15.5y,62.52h,92.77t/data=!3m8!1e1!3m6!1s0FSk6CFvqKNs1NrHEmPd_A!2e0!5s20241101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-2.771208232583689%26panoid%3D0FSk6CFvqKNs1NrHEmPd_A%26yaw%3D62.516048290899796!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIwNC4wIKXMDSoASAFQAw%3D%3D

As anyone seen part-time dual left turn lanes? The left turns don't go onto a road with a reversible lane, nor is one left turn lane an option lane, nor is it in front of a stadium or somewhere else that might experience a short-term surge.

Yeah I don't see the point of it at all. That is a very strange setup.

Many states don't allow double left turns with permissive phasing -  this is done so they can run an FYA in fully protected mode with double left turn lanes for capacity during peak periods, and run it in permissive/protected with a single lane during off peak periods when traffic is lighter.

Interestingly, I believe NC does have a few intersections with dual FYA signals?

[jakeroot]

https://www.google.com/maps/@35.7433314,-78.762743,3a,15.5y,62.52h,92.77t/data=!3m8!1e1!3m6!1s0FSk6CFvqKNs1NrHEmPd_A!2e0!5s20241101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-2.771208232583689%26panoid%3D0FSk6CFvqKNs1NrHEmPd_A%26yaw%3D62.516048290899796!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIwNC4wIKXMDSoASAFQAw%3D%3D

As anyone seen part-time dual left turn lanes? The left turns don't go onto a road with a reversible lane, nor is one left turn lane an option lane, nor is it in front of a stadium or somewhere else that might experience a short-term surge.

Yeah I don't see the point of it at all. That is a very strange setup.

Many states don't allow double left turns with permissive phasing -  this is done so they can run an FYA in fully protected mode with double left turn lanes for capacity during peak periods, and run it in permissive/protected with a single lane during off peak periods when traffic is lighter.

Interestingly, I believe NC does have a few intersections with dual FYA signals?

They do, yes. They are permitted in NC.

For the record, I don't think any single state outright bans double permissive left turns by law. Most states simply have a MUTCD supplement that bans them, which only means they won't appear on state highways. Washington State is like this (even though double left on red is perfectly legal...but that's for another day), but you will find quite a few double permissive left turns on city streets where they don't follow the state MUTCD supplement.

Some states may be more strict on cities doing their own thing, I suppose.

As for the actual desing of the part-time double left turn, I agree they are silly. Just run them permissive by time of day if needed, or run them until there is an apparent issue with crashes.

[roadman65]

https://www.flickr.com/photos/54480415@N08/54350452612
New signals to be installed at Sand Lake Road and Kirkman Road in Orlando are mounted to a highway overhead sign truss and is waiting to lifted into place.

[mrsman]

Here is an interesting setup in Kingman, AZ:

https://www.google.com/maps/@35.1912599,-114.0680111,3a,75y,213.83h,83.55t/data=!3m7!1e1!3m5!1sc84QLEHScz26tSQc7hvZKA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D6.454309238805763%26panoid%3Dc84QLEHScz26tSQc7hvZKA%26yaw%3D213.82796639429046!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MDIyMy4xIKXMDSoJLDEwMjExNDUzSAFQAw%3D%3D

A few years back, this was more straightforward.  Off-ramp from I-40 WB to US 93.  The left lane was straight or left and the right two lanes both were for the right turn movement onto US 93 NB (toward Las Vegas).  As the street (Beale Street) allowed two northbound lanes through the diamond interchange, both right lanes of the exit ramp turned onto the two northbound lanes of US 93.  For a good bit of the time, no turn on red here.

But more recently, they made changes so that only one lane of Beale Street would go through northbound.  (Right lane forced onto on-ramp for I-40 east).  This meant that the far right lane would be a nearly free turn (except for peds) onto US 93 north and the middle lane would be the turn onto the left lane of US 93 north.  The middle lane would still onluy allow a turn with a green right arrow. The right lane does allow a turn at all times, yielding to peds if the signal is red.  And both lanes are now separated between each other with concrete.  (As can be seen in the screen grab, the right lane sees a green arrow, while the middle lane sees a red arrow.)

This is an interesting take on the phenomemon where the curb lane can turn on red, but the center lane would prohibit turns on red (that is common in places like Virginia).  Here each of the two right turn lanes are controlled by separate signals.

[roadman65]

https://www.flickr.com/photos/54480415@N08/54360766083

Really old signal in South Wilmington, DE.

Usually you find these type of old mast arms around Pennsylvania.

[freebrickproductions]

https://www.flickr.com/photos/54480415@N08/54360876410

Really old signal in South Wilmington, DE.

Usually you find these type of old mast arms around Pennsylvania.

I think you meant to link this?
https://www.flickr.com/photos/54480415@N08/54360766083/in/dateposted/

[roadman65]

https://www.flickr.com/photos/54480415@N08/54360876410

Really old signal in South Wilmington, DE.

Usually you find these type of old mast arms around Pennsylvania.

I think you meant to link this?
https://www.flickr.com/photos/54480415@N08/54360766083/in/dateposted/

Yes.

Don't know how I got that one, but that's from a post after I posted this one

Errie like the Twightlight Zone.

But yes

[kphoger]

I don't recall having seen, before this was installed recently, a stoplight facing a gravel road.  How common is that?

https://maps.app.goo.gl/AVeossrVENTiDbu1A

[steviep24]

I don't recall having seen, before this was installed recently, a stoplight facing a gravel road.  How common is that?

https://maps.app.goo.gl/AVeossrVENTiDbu1A

Also, the signal for left turns onto said gravel road is protected only.

[jdbx]

I don't recall having seen, before this was installed recently, a stoplight facing a gravel road.  How common is that?

https://maps.app.goo.gl/AVeossrVENTiDbu1A

That's rather unique.  The places where I have seen a traffic light for an intersecting gravel road, they usually just pave the first 50-100 feet that are adjacent to the intersection.  That probably allows the painting of proper stop lines, placing loop detectors (I see this intersection is camera-controlled), and probably prevents rutting that would happen from the stop/start of heavy vehicles at the light.

[kphoger]

At intersections with four-way split phasing (only one direction of traffic at a time gets a green light), what variation is there in the order of green phases?

Here in Wichita, the Kellogg frontage roads on the east side of town all operate on completely split phasing during daytime hours.  And all of those intersections give green lights in a clockwise manner:  traffic on the north side (SB) gets the green, then traffic on the east side (WB) gets the green, then traffic on the south side (NB) gets the green, then traffic on the west side (EB) gets the green.  I always know my green is coming up soon when traffic coming from my right gets a yellow.

But some other places, surely, operate differently.  Yes?

[jakeroot]

At intersections with four-way split phasing (only one direction of traffic at a time gets a green light), what variation is there in the order of green phases?

Here in Wichita, the Kellogg frontage roads on the east side of town all operate on completely split phasing during daytime hours.  And all of those intersections give green lights in a clockwise manner:  traffic on the north side (SB) gets the green, then traffic on the east side (WB) gets the green, then traffic on the south side (NB) gets the green, then traffic on the west side (EB) gets the green.  I always know my green is coming up soon when traffic coming from my right gets a yellow.

But some other places, surely, operate differently.  Yes?

I think for frontage roads like those in Texas or Wichita, this is pretty much how they operate. Ideally, each ramp terminus would keep their lights green for two of the four phases (eg. southbound traffic and then westbound traffic would both pass through the same green lights at the southern intersection, and then repeat for northbound and eastbound traffic at the northern intersection).

That said, I've never heard of split-phasing for split-phasing's sake. Normally it's done when there is an option lane or overlapping/conflicting turns that necessitate it for safety reasons (so diamond interchange off-ramps or frontage road intersections). And this being the precise reason why SPUIs or DDIs came to be so popular, since they eliminate these conflicts and/or dangers without having to resort to split-phasing.

Here in Japan, our diamond-style intersections have three phases: (1) through traffic on the main road plus right turns yield > (2) protected lagging right turn > (3) off-ramps. In phase 3, the capacity of the off-ramp right turn is limited to the storage space between the two signals, but in practice it's not usually an issue. There is sometimes a fourth phase where one of the off-ramps is cut before the other, to allow the other off-ramp more time to turn without storage issues (basically a right turn into a green light).

Diamond interchange example: https://maps.app.goo.gl/Sod2CWPicPe9L6NA9

Normally, to avoid this mess, SPUIs are preferred, and they operate like most intersections (through traffic plus yielding right turns > protected right turn > off-ramps): https://maps.app.goo.gl/pKDsSkLSYz9DPkZA8 (this example has through lanes for the off-ramp as well, but is otherwise a normal SPUI).

[chrisg69911]

At intersections with four-way split phasing (only one direction of traffic at a time gets a green light), what variation is there in the order of green phases?

Here in Wichita, the Kellogg frontage roads on the east side of town all operate on completely split phasing during daytime hours.  And all of those intersections give green lights in a clockwise manner:  traffic on the north side (SB) gets the green, then traffic on the east side (WB) gets the green, then traffic on the south side (NB) gets the green, then traffic on the west side (EB) gets the green.  I always know my green is coming up soon when traffic coming from my right gets a yellow.

But some other places, surely, operate differently.  Yes?

https://maps.app.goo.gl/guEzzBVbfugtaB5a7
Here the phasing operates in a counterclockwise manner, the road to your left will always have the green before you. It is set up though that when an offramp gets the green, the direction of the left turn on Moonachie Ave also gets a green to have no backups.

And just on an unrelated note, I always find it ridicoulus/funny that some states build massive bridges, 12 lanes in your case, and in every street view, there isn't ever enough traffic to justify that many lanes. Call me crazy, but dual right turn, dual left turn, and three through lanes are never needed.

[kphoger]

I've never heard of split-phasing for split-phasing's sake.

I see it all the time in Mexico... 

Here in Japan ... In phase 3, the capacity of the off-ramp right turn is limited to the storage space between the two signals, but in practice it's not usually an issue.

I'm sure this is precisely why these intersections on E Kellogg are completely split-phased.  A few of them would definitely have storage problems, especially at rush hour.

[roadfro]

Here in Japan ... In phase 3, the capacity of the off-ramp right turn is limited to the storage space between the two signals, but in practice it's not usually an issue.

I'm sure this is precisely why these intersections on E Kellogg are completely split-phased.  A few of them would definitely have storage problems, especially at rush hour.

There are signal phasing schemes for these scenarios (typically employed at diamond interchanges) that can reduce storage problems while not being completely split phased. I'm recalling "TTI 4-phase" from learning about it in college years ago, but can't recall the other.

[kphoger]

There are signal phasing schemes for these scenarios (typically employed at diamond interchanges) that can reduce storage problems while not being completely split phased. I'm recalling "TTI 4-phase" from learning about it in college years ago, but can't recall the other.

As for tight diamonds?  Yes, we have some of those too.