Traffic signal

[jakeroot]

Also there's this doghouse variant (idk the actual name of it) with a missing yellow left signal that I sometimes see in Columbus. Not sure how it works; does the yellow left arrow share the same section as the yellow ball?

That's just a split-phase signal where the bottom green arrow was moved up, likely for clearance issues or because of that power line (signal in Fife, WA installed for the same reason). Nothing to do with doghouse signals.

I personally prefer this style, but that's neither here nor there.

I'm still a traditional doghouse fan, because of the symmetry.

Totally fair. My preference is simply because I like to keep the circular indications in a line. I don't understand why the red is centered at all. It's not like symmetry matters to engineers.

[SkyPesos]

Also there's this doghouse variant (idk the actual name of it) with a missing yellow left signal that I sometimes see in Columbus. Not sure how it works; does the yellow left arrow share the same section as the yellow ball?

That's just a split-phase signal where the bottom green arrow was moved up, likely for clearance issues or because of that power line (signal in Fife, WA installed for the same reason). Nothing to do with doghouse signals.

This is the first time I've seen a split phase signal with one of the two movements missing on the green then. Kind of wondering if this is supposed to be similar to Ontario's split phase signals, with a protected-permissive left turn option. Or if it's just an electrical issue, since every other green phase of that exact signal I've seen on GSV have both the left arrow and bulb working.

[jakeroot]

Also there's this doghouse variant (idk the actual name of it) with a missing yellow left signal that I sometimes see in Columbus. Not sure how it works; does the yellow left arrow share the same section as the yellow ball?

That's just a split-phase signal where the bottom green arrow was moved up, likely for clearance issues or because of that power line (signal in Fife, WA installed for the same reason). Nothing to do with doghouse signals.

This is the first time I've seen a split phase signal with one of the two movements missing on the green then. Kind of wondering if this is supposed to be similar to Ontario's split phase signals, with a protected-permissive left turn option. Or if it's just an electrical issue, since every other green phase of that exact signal I've seen on GSV have both the left arrow and bulb working.

You were right the first time. That is indeed a protected-permissive bimodal arrow. All evidence pointed to split phasing (note the other direction has a protected left), but your GSV pretty clearly shows it operating permissively (crosswalk signal being active on the left is the big giveaway). There are many four-section bimodal left turn signals out there (very common in parts of WA), but I cannot recall seeing any in this configuration. I definitely don't see why a doghouse wasn't used, especially given the other adjacent signal.

edit: it may not necessarily be bimodal. The oncoming left did not use to exist. It's possible this was a lagging green arrow at one point, which would not have required a yellow arrow. But when they switched it to leading (the case based on this GSV still where both directions have a yellow at the same time), they may not have realized that the yellow arrow was missing. Or maybe they went back and made it bimodal...who knows.

[JoePCool14]

I personally prefer this style, but that's neither here nor there.

I'm still a traditional doghouse fan, because of the symmetry.

Totally fair. My preference is simply because I like to keep the circular indications in a line. I don't understand why the red is centered at all. It's not like symmetry matters to engineers.

Engineers may not care about symmetry, but we do care about aesthetics (sometimes).

[mrsman]

Also there's this doghouse variant (idk the actual name of it) with a missing yellow left signal that I sometimes see in Columbus. Not sure how it works; does the yellow left arrow share the same section as the yellow ball?

That's just a split-phase signal where the bottom green arrow was moved up, likely for clearance issues or because of that power line (signal in Fife, WA installed for the same reason). Nothing to do with doghouse signals.

This is the first time I've seen a split phase signal with one of the two movements missing on the green then. Kind of wondering if this is supposed to be similar to Ontario's split phase signals, with a protected-permissive left turn option. Or if it's just an electrical issue, since every other green phase of that exact signal I've seen on GSV have both the left arrow and bulb working.

You were right the first time. That is indeed a protected-permissive bimodal arrow. All evidence pointed to split phasing (note the other direction has a protected left), but your GSV pretty clearly shows it operating permissively (crosswalk signal being active on the left is the big giveaway). There are many four-section bimodal left turn signals out there (very common in parts of WA), but I cannot recall seeing any in this configuration. I definitely don't see why a doghouse wasn't used, especially given the other adjacent signal.

edit: it may not necessarily be bimodal. The oncoming left did not use to exist. It's possible this was a lagging green arrow at one point, which would not have required a yellow arrow. But when they switched it to leading (the case based on this GSV still where both directions have a yellow at the same time), they may not have realized that the yellow arrow was missing. Or maybe they went back and made it bimodal...who knows.

I agree that it is probably really hard to guess at what the signal mode configuration is there at that intersection, unless someone is nearby and can watch the operation.

First, I think jakeroot is correct that the configuration of the aspects, where the arrow is to the left of the green orb, is likely for clearance considerations.  Operationally, the signal is no different that a 4 aspect tower: R-Y-G-?

When I do see a 4 aspect tower, these are the possibilities that I think of (in order) unless other evidence points otherwise:

Split phase
Lagging left (no longer allowed without separate yellow arrow*, but many w/o yellow arrow still exist)
Leading left with bimodal arrrow
Leading left with a missing yellow arrow aspect (not great, but they do still exist, but are rare).

Of these, I believe this is probably the second of these possibilities, the lagging left.  First, in the pre-FYA era, it was very common to signal lead-lag signals with the leading left on a protected only signal and the lagging left permissive.   This was to prevent yellow trap on the leading side during the lagging phase.  Second, the GSVs showing simultaneous yellow do rule out split-phasing, but do not necessarily rule out lagging left.  It could be that since the lagging left is permissive, the lagging left is only shown when it is needed.  But on that still, while there are a lot of cars wanting to turn left on the protected side (and they can't because of the red arrow), there are no cars waiting to turn left on the lagging side.  If there are good sensors here, the lagging left would only be triggered when there is a need to trigger the lagging left, i.e. cars waiting to turn.  And one thing about a lagging left is that while there may be a bunch of cars needing to make the turn at the beginning of the cycle, if they are all able to find a gap in opposing traffic to make their turns there would be no need to even provide the protected arrow at the end of the cycle.  And that is better for most everyone, because providing protected lefts takes away proportionate signal time from the other phases, so to the extent that one of the signal phases can be safely skipped, it is better for everyone else, namely the thru traffic.

Of course, all of the above is speculation, as I have not been at this intersection in Columbus.  BOth sides leading left is also possible, but it is hard to believe that they would implement that without a yellow arrow.


*IMO for a lagging left the yellow arrow is really not necessary, since the yellow arrow time would be shown at the exact same times as the yellow orb.  For whatever reasons more recent editions of MUTCD require a yellow arrow for lagging lefts but don't require them for split-phasing.

[PurdueBill]

I'm looking at some Phoenix SPUIs from the discussion from a week ago, and found a straight movement red light with an up arrow. This is common in some other countries, like China, but it's the first time seeing one in the states for me. Any other examples of this?

The straight red arrow is disallowed because a red ball would be easier to see than a red arrow.

What's also interesting about this signal is that it is also a bus signal.  Apparently, buses along SR-51 are encouraged to exit and then continue back on the freeway.  I guess they feel it is quicker for buses to do that in heavy traffic periods.  What's interesting is that there is no provision for that in the other direction.  What is also interesting is that there is no bus stop at that point.  In LA, freewaay buses that exit usually do so to service an exit.  Here is an example of a freeway bus along US 101 that exits at Van Nuys Blvd at a diamond interchange, continues straight across the street and then makes a stop just before the on-ramp.

Bus stop shown, not the bus itself.

https://www.google.com/maps/@34.1562833,-118.4478097,3a,37.5y,141.57h,87.25t/data=!3m6!1e1!3m4!1sEWnqDJvSWCYtNAVATFqFtw!2e0!7i16384!8i8192

Right away I thought of the first signal you hit on US 36 in Boulder entering town; I have a photo of it that I got in 2016 but the street view is clearer probably.

https://goo.gl/maps/zcRu6mFx98A5Fhfm9

It is to emphasize no right turns as the frontage road is there.  They didn't go all-out; just the one with the rest red balls.
There were lots of other interesting things around there (fairly modern 12-8-8s; doghouses with red arrows at the top) as well.

[roadman65]

What's with the double red lights here in NC? Does it mean to stop only by looking at 2 red lights?

Double reds are an option that some states use more than others (Texas in particular). It has no special meaning.

San Antonio don't use double red signals.

A lot of Texas doesn't, but the number of double reds in other parts likely outnumbers the total number in most other states put together. I can think of two or three double reds in all of Washington.

Houston probably has more signals than the whole state of Wyoming.

[roadman65]

Don't ask me what happened. I deleted the part I wasn't responding to and got this.

[kphoger]

Don't ask me what happened. I deleted the part I wasn't responding to and got this.

Your reply went before the final [/quo.te] tag rather than after it.

[SkyPesos]

I agree that it is probably really hard to guess at what the signal mode configuration is there at that intersection, unless someone is nearby and can watch the operation.

First, I think jakeroot is correct that the configuration of the aspects, where the arrow is to the left of the green orb, is likely for clearance considerations.  Operationally, the signal is no different that a 4 aspect tower: R-Y-G-?

When I do see a 4 aspect tower, these are the possibilities that I think of (in order) unless other evidence points otherwise:

Split phase
Lagging left (no longer allowed without separate yellow arrow*, but many w/o yellow arrow still exist)
Leading left with bimodal arrrow
Leading left with a missing yellow arrow aspect (not great, but they do still exist, but are rare).

Of these, I believe this is probably the second of these possibilities, the lagging left.  First, in the pre-FYA era, it was very common to signal lead-lag signals with the leading left on a protected only signal and the lagging left permissive.   This was to prevent yellow trap on the leading side during the lagging phase.  Second, the GSVs showing simultaneous yellow do rule out split-phasing, but do not necessarily rule out lagging left.  It could be that since the lagging left is permissive, the lagging left is only shown when it is needed.  But on that still, while there are a lot of cars wanting to turn left on the protected side (and they can't because of the red arrow), there are no cars waiting to turn left on the lagging side.  If there are good sensors here, the lagging left would only be triggered when there is a need to trigger the lagging left, i.e. cars waiting to turn.  And one thing about a lagging left is that while there may be a bunch of cars needing to make the turn at the beginning of the cycle, if they are all able to find a gap in opposing traffic to make their turns there would be no need to even provide the protected arrow at the end of the cycle.  And that is better for most everyone, because providing protected lefts takes away proportionate signal time from the other phases, so to the extent that one of the signal phases can be safely skipped, it is better for everyone else, namely the thru traffic.

Of course, all of the above is speculation, as I have not been at this intersection in Columbus.  BOth sides leading left is also possible, but it is hard to believe that they would implement that without a yellow arrow.


*IMO for a lagging left the yellow arrow is really not necessary, since the yellow arrow time would be shown at the exact same times as the yellow orb.  For whatever reasons more recent editions of MUTCD require a yellow arrow for lagging lefts but don't require them for split-phasing.

So I guess this is different from how Ontario does their 4 section protected-permissive signals, which according to their guide, it's a leading left, with the yellow left arrow sharing the same signal section as the green left arrow. My first thought of seeing the Columbus one was Ontario's, but I'm not sure if the MUTCD allows that for leading lefts, but only for lagging lefts as you described.

[jakeroot]

I agree that it is probably really hard to guess at what the signal mode configuration is there at that intersection, unless someone is nearby and can watch the operation.

First, I think jakeroot is correct that the configuration of the aspects, where the arrow is to the left of the green orb, is likely for clearance considerations.  Operationally, the signal is no different that a 4 aspect tower: R-Y-G-?

When I do see a 4 aspect tower, these are the possibilities that I think of (in order) unless other evidence points otherwise:

Split phase
Lagging left (no longer allowed without separate yellow arrow*, but many w/o yellow arrow still exist)
Leading left with bimodal arrrow
Leading left with a missing yellow arrow aspect (not great, but they do still exist, but are rare).

Of these, I believe this is probably the second of these possibilities, the lagging left.  First, in the pre-FYA era, it was very common to signal lead-lag signals with the leading left on a protected only signal and the lagging left permissive.   This was to prevent yellow trap on the leading side during the lagging phase.  Second, the GSVs showing simultaneous yellow do rule out split-phasing, but do not necessarily rule out lagging left.  It could be that since the lagging left is permissive, the lagging left is only shown when it is needed.  But on that still, while there are a lot of cars wanting to turn left on the protected side (and they can't because of the red arrow), there are no cars waiting to turn left on the lagging side.  If there are good sensors here, the lagging left would only be triggered when there is a need to trigger the lagging left, i.e. cars waiting to turn.  And one thing about a lagging left is that while there may be a bunch of cars needing to make the turn at the beginning of the cycle, if they are all able to find a gap in opposing traffic to make their turns there would be no need to even provide the protected arrow at the end of the cycle.  And that is better for most everyone, because providing protected lefts takes away proportionate signal time from the other phases, so to the extent that one of the signal phases can be safely skipped, it is better for everyone else, namely the thru traffic.

Of course, all of the above is speculation, as I have not been at this intersection in Columbus.  BOth sides leading left is also possible, but it is hard to believe that they would implement that without a yellow arrow.


*IMO for a lagging left the yellow arrow is really not necessary, since the yellow arrow time would be shown at the exact same times as the yellow orb.  For whatever reasons more recent editions of MUTCD require a yellow arrow for lagging lefts but don't require them for split-phasing.

So I guess this is different from how Ontario does their 4 section protected-permissive signals, which according to their guide, it's a leading left, with the yellow left arrow sharing the same signal section as the green left arrow. My first thought of seeing the Columbus one was Ontario's, but I'm not sure if the MUTCD allows that for leading lefts, but only for lagging lefts as you described.

So the MUTCD is actually pretty flexible when it comes to left turn operation. Even yellow trap is still permitted, IIRC.

Based on mrsman's analysis, it would seem that the Ohio intersection/left turn you posted may not have a yellow arrow (so not quite like the Ontario examples you are familiar with), but because the green arrow would only display at the end, using the yellow orb to clear traffic rather than a yellow arrow (as would be required if the left turn were leading and the green orb was already being displayed).

Intersections that operate like this are not unusual. In fact, at one-way streets in many west and east coast cities, 4-section protected-permissive signals are the norm (example from Spokane, WA). Because the left turns are always lagging, or skipped, there is no need for a yellow arrow because the end of the protected left turn phase will always coincide with the end of the through phase.

Leading left turns that have only four sections, like those in Canada (the Ontario setup, with a flashing green arrow and solid yellow arrow in a single aspect, is used across Canada and was actually pioneered outside Ontario), are actually quite common in parts of the US. Here in Tacoma, probably half of all left turns that use "yield-on-green" phasing use bimodal green/yellow arrows (good example here showing opposing green arrows). I don't know why these are used in place of 5-section "yield-on-green" signals, but they are very common nonetheless. Importantly, a shared signal face is absolutely allowed by the MUTCD for left turn arrows. Canada's variation is only different because of the flashing green arrow. But then they rarely use 5-section left turn signals, so something to improve the 4-section design was necessary. Here in the US, rather than innovate similarly, we decided to jump ship and adopt the FYA.

[jakeroot]

I thought this was pretty nifty.

The interchange between I-5 and 116 St NE in Marysville, WA was recently rebuilt from a diamond into a SPUI. However, unlike most SPUIs, there was a need for a through movement because of buses that use the ramps.

So to allow the buses to access the stops on the ramps, 8-8-8 right-angled arrows were installed specifically for the buses. When the buses get a green arrow, they make a sort-of 90 degree turn back onto the on-ramp and then stop.

I suppose the backplates could have been dropped, but WSDOT had a spec for those from all the 8-inch signals used at ramp meters.

[hotdogPi]

Horizontal signal found in Massachusetts, of all places:
https://www.google.com/maps/@42.3399814,-71.0631048,3a,75y,70.07h,95.72t/data=!3m6!1e1!3m4!1shhEY6PKAQF48KhyzUvcRaw!2e0!7i16384!8i8192

[Amtrakprod]

Horizontal signal found in Massachusetts, of all places:
https://www.google.com/maps/@42.3399814,-71.0631048,3a,75y,70.07h,95.72t/data=!3m6!1e1!3m4!1shhEY6PKAQF48KhyzUvcRaw!2e0!7i16384!8i8192

Nice find! I only knew about this one in Dedham


iPhone

[CoreySamson]

Nice find! I only knew about this one in Dedham


iPhone

Interesting, I wonder why the signals are suspended below the pole like that. All other pole-mounted horizontal signals I've seen have the signals mounted right on the pole like this.

[SkyPesos]

Nice find! I only knew about this one in Dedham


iPhone

Interesting, I wonder why the signals are suspended below the pole like that. All other pole-mounted horizontal signals I've seen have the signals mounted right on the pole like this.

Probably because of an overhead crossing at or right before the stop line that blocks vision from vertical signals or horizontal signals mounted on the pole.

Also, why are there two left red arrows per signal in your example?

[CoreySamson]

...signals mounted right on the pole like this.

Also, why are there two left red arrows per signal in your example?

Guess you've never been to Texas before.  Down here, it's the norm for left turn signals to have a double red to differentiate them from thru signals. Usually, it doesn't matter whether the double red is arrows or just orbs (though it seems the newer examples are arrows), so you can get some strange scenarios such as this, where the first light has arrows, but the second light has orbs. At most lights there is no left turn yield phase, though I am starting to see the flashing yellow appear in some places (I think it works great with this setup).

To further complicate things, there's this junction near Sweeny where they used the double red for each signal, not just the turn signals (the turn signal has arrows, while the main lanes have orbs). It's either an error or designed that way for visibility reasons, but I don't really like it (jakeroot probably remembers my beef about this signal in another thread).

[jakeroot]

To further complicate things, there's this junction near Sweeny where they used the double red for each signal, not just the turn signals (the turn signal has arrows, while the main lanes have orbs). It's either an error or designed that way for visibility reasons, but I don't really like it (jakeroot probably remembers my beef about this signal in another thread).

I remember now, but only after looking through your post history.

It is rather odd to me that double reds for turn signals would be so common in Texas that any other double reds would likely be automatically identified by Average Joe as a turn signal. But every state has its own oddities, so who am I to judge?

[UnumProvident101]

at this intersection in Red Bank, TN there used to be a third traffic light but it was removed about a couple of years ago
https://www.google.com/maps/@35.0840473,-85.3176384,3a,90y,41.42h,84.57t/data=!3m6!1e1!3m4!1s_i_zqSeV3E7gss2zuktXyg!2e0!7i13312!8i6656

May 2014
https://www.google.com/maps/@35.0840244,-85.3176173,3a,75y,38.94h,84.23t/data=!3m7!1e1!3m5!1smVliznd5Nvhwb4_2ELocuA!2e0!5s20140501T000000!7i13312!8i6656

[jakeroot]

at this intersection in Red Bank, TN there used to be a third traffic light but it was removed about a couple of years ago
https://www.google.com/maps/@35.0840473,-85.3176384,3a,90y,41.42h,84.57t/data=!3m6!1e1!3m4!1s_i_zqSeV3E7gss2zuktXyg!2e0!7i13312!8i6656

May 2014
https://www.google.com/maps/@35.0840244,-85.3176173,3a,75y,38.94h,84.23t/data=!3m7!1e1!3m5!1smVliznd5Nvhwb4_2ELocuA!2e0!5s20140501T000000!7i13312!8i6656

"Protected turn on green arrow only" seems like an odd variation I've not seen before. Seems kind of redundant, as a green arrow means protected turn. Obviously.

[Caps81943]

What is the point of having dueling three-section FYA's like at this intersection in Indiana? Is it just to give opposing traffic a leadoff (via red left-turn arrows) to prevent accidents?

https://www.google.com/maps/@40.3026994,-86.1268606,3a,18.3y,0.5h,92.58t/data=!3m6!1e1!3m4!1sTqgmVDMsHvpVvGhrSmexdw!2e0!7i16384!8i8192

[UCFKnights]

What is the point of having dueling three-section FYA's like at this intersection in Indiana? Is it just to give opposing traffic a leadoff (via red left-turn arrows) to prevent accidents?

https://www.google.com/maps/@40.3026994,-86.1268606,3a,18.3y,0.5h,92.58t/data=!3m6!1e1!3m4!1sTqgmVDMsHvpVvGhrSmexdw!2e0!7i16384!8i8192

A few intersections around here were switched to that because it reinforces that you need to yield to straight traffic a whole lot better then the previous sign did. However, they did it at intersections where there wasn't a whole lot of straight movement.

[UnumProvident101]

I've seen this intersection before in Chattanooga, TN but one of the traffic lights only allow about 1 to 2 cars to go through
https://www.google.com/maps/@35.151582,-85.2184562,3a,85y,194.01h,69.95t/data=!3m6!1e1!3m4!1s5j54iS-FgFh23znsPsjwkA!2e0!7i13312!8i6656

[roadman65]

https://goo.gl/maps/MjPvshr46sN6v63A7
Workers present redoing a signal head with assembly removed.

[Caps81943]

I actually stumbled upon a signal retrofit near my place a few weeks ago while running an errand. In your head you know they happen ("hey, this light wasn't an FYA yesterday"), but it was still really odd to see one in action, especially since, aside from a closed lane, the signal was still up and running.