Traffic signal

[roadfro]

Rather unusual situation. Curious if it's MUTCD compliant?

At this intersection in Tacoma, WA, traffic is permitted to go three directions: straight-on, slight left, and hard left. At the beginning of the phase, there is a protected green arrow for the slight left turn, to coincide with that direction's green movement, but the hard left turn "must yield" (as the slightly-angled green arrow only protects the slight left turn). This is followed by a permissive phase for the slight left (the hard left remaining as fully-permissive).

My question is whether or not it's acceptable to permit this situation. My worries arise because of the green arrow in combination with the "must yield" action for the hard left, and that both movements occur from the same lane.

IMHO, I would go with MUTCD compliant, given the angle of the green arrow - but I would love to see FHWA's take on it.  It would be similar to many cases where a left turn would protected, but a U-turn would have to yield.

Hopefully the next edition of the MUTCD will have more discussion of this and other non-standard intersections (such as how to do signal warrants for this intersection and/or those with five or more legs).

I'm not 100% sure it's compliant, but also not 100% sure that it isn't. It's one of those situations that sufficiently unusual that you can't come up with a "typical" scenario to put into the MUTCD. It also doesn't help that both left turns are made from the same lane, so you can't separate the operation.

The only way I can think of to improve this and also remove the ambiguity with the sign is to use a modified doghouse. In the left column would be FYA for the hard left, and the right column would display green and FYA arrows for the slight left. (This solution would need to introduce an additional through signal to maintain compliance with the MUTCD standard about two through signals.)

So for both the Nashua, NH and Tacoma, WA intersections, something like this?



The topmost section is a red ball, the upper yellow sections are for clearance, and the bottom green/yellow bimodal section is for the protected and permissive movements. The "LEFT TURN SIGNAL" sign is only there because in the Nashua example, the left turn from WB NH-101A to WB NH-130 cannot proceed when the opposing (eastbound NH-101A) traffic has a green, which results in a red ball for the left turn onto 130, and straight-arrow for traffic proceeding on 101A west.

You'll have a single signal for each movement, when 2 signals per movement are preferred.

Really, this is an issue regarding lane assignments or phasing.  If you take the right lane and make that the straight/soft left movement, and make the left lane the hard left movement, then you can dedicate the signal for the left lane for the hard left, and dedicate the signals for the right lane for the other two movements, then everything is MUTCD kosher.  Likewise, if you add an additional phase where traffic from the soft left has it's own phase, then traffic in the left lane pictured above can turn left hard or soft without interference.

Yet, there are issues with the above.  If traffic volumes warrant the two lanes, there may be too much traffic going straight and making the soft left to stuff in one lane.  How do you show the signal for the hard left - a solid green arrow indicates they have priority, which isn't true.  This is where a FYA works well, due to the unusual intersection layout.   Also, it may feel unnatural to make that soft left from the right lane, confusing motorists.  Or, if you add an additional cycle, then that creates more waiting time for traffic, adding potential delay and congestion to the intersection.

Intersections like this are tough to deal with, and any option presented has downsides.

Yeah fwydriver, that's kinda what I envisioned, just not the U-turn arrow version. Although I would maybe use a louvered circular red on that left turn head to avoid a "left turn signal" sign.

jeffandnicole is right that there's really an issue with phasing or lane assignment here that contributes to the problem, and there won't be an elegant solution if you can't get each movement to have a dedicated lane.

I suspect the hard left in these cases is a more minor movement, so making both lefts from the left lane promotes lane balance on the approach. It also helps with phasing, because the through direction is able to run with any phase other than the side street/conflicting peds. But this gives us the awkward signal arrangement.

[mrsman]

Rather unusual situation. Curious if it's MUTCD compliant?

At this intersection in Tacoma, WA, traffic is permitted to go three directions: straight-on, slight left, and hard left. At the beginning of the phase, there is a protected green arrow for the slight left turn, to coincide with that direction's green movement, but the hard left turn "must yield" (as the slightly-angled green arrow only protects the slight left turn). This is followed by a permissive phase for the slight left (the hard left remaining as fully-permissive).

My question is whether or not it's acceptable to permit this situation. My worries arise because of the green arrow in combination with the "must yield" action for the hard left, and that both movements occur from the same lane.

IMHO, I would go with MUTCD compliant, given the angle of the green arrow - but I would love to see FHWA's take on it.  It would be similar to many cases where a left turn would protected, but a U-turn would have to yield.

Hopefully the next edition of the MUTCD will have more discussion of this and other non-standard intersections (such as how to do signal warrants for this intersection and/or those with five or more legs).

I'm not 100% sure it's compliant, but also not 100% sure that it isn't. It's one of those situations that sufficiently unusual that you can't come up with a "typical" scenario to put into the MUTCD. It also doesn't help that both left turns are made from the same lane, so you can't separate the operation.

The only way I can think of to improve this and also remove the ambiguity with the sign is to use a modified doghouse. In the left column would be FYA for the hard left, and the right column would display green and FYA arrows for the slight left. (This solution would need to introduce an additional through signal to maintain compliance with the MUTCD standard about two through signals.)

So for both the Nashua, NH and Tacoma, WA intersections, something like this?



The topmost section is a red ball, the upper yellow sections are for clearance, and the bottom green/yellow bimodal section is for the protected and permissive movements. The "LEFT TURN SIGNAL" sign is only there because in the Nashua example, the left turn from WB NH-101A to WB NH-130 cannot proceed when the opposing (eastbound NH-101A) traffic has a green, which results in a red ball for the left turn onto 130, and straight-arrow for traffic proceeding on 101A west.

You'll have a single signal for each movement, when 2 signals per movement are preferred.

Really, this is an issue regarding lane assignments or phasing.  If you take the right lane and make that the straight/soft left movement, and make the left lane the hard left movement, then you can dedicate the signal for the left lane for the hard left, and dedicate the signals for the right lane for the other two movements, then everything is MUTCD kosher.  Likewise, if you add an additional phase where traffic from the soft left has it's own phase, then traffic in the left lane pictured above can turn left hard or soft without interference.

Yet, there are issues with the above.  If traffic volumes warrant the two lanes, there may be too much traffic going straight and making the soft left to stuff in one lane.  How do you show the signal for the hard left - a solid green arrow indicates they have priority, which isn't true.  This is where a FYA works well, due to the unusual intersection layout.   Also, it may feel unnatural to make that soft left from the right lane, confusing motorists.  Or, if you add an additional cycle, then that creates more waiting time for traffic, adding potential delay and congestion to the intersection.

Intersections like this are tough to deal with, and any option presented has downsides.

Yeah fwydriver, that's kinda what I envisioned, just not the U-turn arrow version. Although I would maybe use a louvered circular red on that left turn head to avoid a "left turn signal" sign.

jeffandnicole is right that there's really an issue with phasing or lane assignment here that contributes to the problem, and there won't be an elegant solution if you can't get each movement to have a dedicated lane.

I suspect the hard left in these cases is a more minor movement, so making both lefts from the left lane promotes lane balance on the approach. It also helps with phasing, because the through direction is able to run with any phase other than the side street/conflicting peds. But this gives us the awkward signal arrangement.

It's not just awkward, it's dangerous.  The minor movement is in conflict with traffic that is coming from the opposing right turn.  Many people would not be expecting traffic coming from their side, especially if they are facing what amounts to a green arrow.

IMO the only safe options for the Tacoma signal would be: 1) Prohibition of left onto Yakima or 2) Protected left for both 1st and Yakima, and traffic coming from 1st with right onto Division must have a separate phase.

While functionally, the situation is equivalent to one who makes a u-turn at a signal with protected lefts concurrent with protected rights* (or left turns into a driveway just in front of an intersection with a protected left concurrent with protected right), the situation is unique enough that it could lead to confustion.  Since you don't want cars turning left from Division onto Yakima thinking they have a protected left, the left must be prohibited.

* As noted some states (like CA) prohibit u-turns where there is a concurrent right turn.  I agree with this practice since it is much safer.  Some states allow the practice, but put in signage to have u-turns yield to right turns.  Here in MD, u-turns are routinely allowed in such situations, and the really busy u-turn intersections may have a u-turn yield sign, but not commonly.

[ErmineNotyours]

Here's video of a five-way intersection I have mentioned before: Langston, Hardie and Sunset in Renton, Washington.  The 3M'ed permissive left comes on when the soft left Langston gets a green, and is intended for hard lefts onto Sunset. [edit: That lane is intended for both lefts onto both streets.]  It's an older light and would have been a flashing yellow arrow if it were installed today.  At the start of the video we see traffic in the middle lane trying to turn onto Langston and causing lefts from Hardie to turn behind them.  Location on Google Maps.

(This is the first time I used the slightly higher bit rate on this camera, and I couldn't even get the video to play on my computer.  It loaded to YouTube, but without sound.)

https://youtu.be/iGj7pM0zn48

[SignBridge]

Surprised to see Dallas Phasing in Renton, Washington. (Green ball over left-turn lane with red over thru lanes) I thought that was only used in Texas. And yes, today a flashing-yellow arrow would be required for that application.

[jeffandnicole]

News flash...a flashing yellow is NEVER required. It's sinply another option to utilize when appropriate.

[ErmineNotyours]

Also taken today, something I had been thinking about photographing for years.  Looking down South 2nd Street, a one-way street with synchronized lights, I occasionally noticed you can see them all green for a brief time.  Lately this has been complicated by the changed timing of the Main Street light in front, but wait long enough you can see them all green.  A bus got in the way of some of the lights, and I gave up waiting for things to line up again.

[jakeroot]

News flash...a flashing yellow is NEVER required. It's sinply another option to utilize when appropriate.

It would be required for the above application, however, assuming Renton wanted to keep it permissive.

IMO the only safe options for the Tacoma signal would be: 1) Prohibition of left onto Yakima or 2) Protected left for both 1st and Yakima, and traffic coming from 1st with right onto Division must have a separate phase.

I'm not sure if I mentioned this or not, but there will be a trolley running along 1st within the next couple of years. I'm not sure how the intersection will be modified to incorporate this modification, but I know it will involve flashing yellow arrows. I don't remember where I read that (News Tribune, I think), but I know someone asked the city about flashing yellow arrows in general within the last 12 months, and they mentioned this intersection as being a place that will have flashing yellow arrows in the future.

[jeffandnicole]

News flash...a flashing yellow is NEVER required. It's sinply another option to utilize when appropriate.

It would be required for the above application, however, assuming Renton wanted to keep it permissive.

All the flashing yellow arrow is, is the historic 'yield on green'.

Find me a law, statute or ruling that says Flashing Yellow arrow is required.

Some states don't even use flashing yellow arrows yet.

And to be technical, all the light needs to be is red/yellow/green.  Arrows of any sort aren't required, and is based on an engineering study or guidance.  Heck, a light isn't even required either.  They could have stop signs at these intersections!

[fwydriver405]

News flash...a flashing yellow is NEVER required. It's sinply another option to utilize when appropriate.

It would be required for the above application, however, assuming Renton wanted to keep it permissive.

All the flashing yellow arrow is, is the historic 'yield on green'.

Find me a law, statute or ruling that says Flashing Yellow arrow is required.

Some states don't even use flashing yellow arrows yet.

And to be technical, all the light needs to be is red/yellow/green.  Arrows of any sort aren't required, and is based on an engineering study or guidance.  Heck, a light isn't even required either.  They could have stop signs at these intersections!

Doesn't MUTCD Chapter 4d.18.02 prohibit circular green in separate left turn faces over the left turn lane, which essentially prohibits Dallas Phasing?

02 If a separate left-turn signal face is being operated in a permissive only left-turns mode, a CIRCULAR GREEN signal indication shall not be used in that face.

[jakeroot]

Find me a law, statute or ruling that says Flashing Yellow arrow is required.

Man, you are being real dense. If the city of Renton wants to continue operating the left turns with permissive phasing, and it wants to run that far left turn separate from the other left turn, it would need to use a flashing yellow arrow because Dallas Phasing is no longer permitted.

The FYA was not invented for shits and giggles. It has very specific advantages over traditional "yield on green" signals. And while you are correct, it is not "required", it is a city's only option in scenarios like the above video in Renton, assuming the far left turn lane needs to run separately and with permissive phasing (in other words, exactly how it operates right now).

[SignBridge]

Jakeroot is correct. As per the Manual, if left turns are permitted while the thru lanes have a red light, a green-arrow or FYA must be used. A green-ball can be used only as part of a so-called "shared-signal" (see the MUTCD for definition) over the line separating the turn-lane from the thru-lane and must show green for all lanes in the same direction at the same time.

I'm kind of surprised that our friend J&N who is usually a very helpful participant on this board is being so argumentative today. LOL

[jeffandnicole]

Jakeroot is correct. As per the Manual, if left turns are permitted while the thru lanes have a red light, a green-arrow or FYA must be used. A green-ball can be used only as part of a so-called "shared-signal" (see the MUTCD for definition) over the line separating the turn-lane from the thru-lane and must show green for all lanes in the same direction at the same time.

I'm kind of surprised that our friend J&N who is usually a very helpful participant on this board is being so argumentative today. LOL

I was more hung up on the "required" use of the FYA.

Reviewing the video again, I see a bit more what's happening. It's just a messed up situation. I now see the left lane has it's own green but left turning traffic has to yield. But to compound it, traffic in the left they lane also makes a left turn. It's probably a situation where the locals have made their own traffic pattern.

(Yeah, I'm sure I'm just repeating what you already know)

There are some ways to deal with this without a FYA, but it will mostly be at the expense of adding another phase to the cycle.

[jakeroot]

There are some ways to deal with this without a FYA, but it will mostly be at the expense of adding another phase to the cycle.

But that was kind of my point. To operate the intersection exactly the way that it operates right now, it would need an FYA. Sure, you could add or delete this or that phase, and in a world without the FYA, that's probably what would happen (assuming Dallas Phasing was eliminated as an option but not replaced by anything else). But given that a separate left-turn signal with permissive phasing was actually invented (the FYA), this just so happens to be the exact kind of situation where that kind of signal would need to be installed (again, to operate it the same way that it was before).

[kphoger]

It appears we have now found a case that makes the invention of the FYA 100% justified.  All the haters can now bite their tongues.   

[traffic light guy]

I found some old Eagles on angled mast-arms the other day:

Old Eagles on an angled mast-arm by thesignalman, on Flickr

Old Eagles on an angled mast-arm by thesignalman, on Flickr

Old Eagles on an angled mast-arm by thesignalman, on Flickr


You don't find setups like these too often nowadays, especially an intersection like this, which still has the original signal heads intact. I think PA was one of the few states to do the practice of mounting signals using poles that were slanted at 45-degree angle.

[MNHighwayMan]

I found some old Eagles on angled mast-arms the other day:

Now let's play the game of "How many more relevant threads can I post these pictures to?"

[traffic light guy]

I found some old Eagles on angled mast-arms the other day:

Now let's play the game of "How many more relevant threads can I post these pictures to?"

Only two, just this and old traffic signals

LG-M327

[ErmineNotyours]

Lowest mounted traffic signal I have ever seen (not counting signals used by railroads).  At least it is on an island prohibiting pedestrians, otherwise it would be low enough to touch.

[ErmineNotyours]

Two lefts and one right.

[jakeroot]

Two lefts and one right.

Probably there to satisfy the "two signals for through and/or dominant movement" rule.

[Revive 755]

Speaking of angled mast arms, there's this one on EB IL 62 in Rolling Meadows (Chicagoland)

[jakeroot]

How often are traffic signal heads and pedestrian heads mounted at the same level?

I see this in British Columbia but not so often in the US. This image is from Tacoma, WA (mid-block crossing over a tram track):

[Big John]

^^

MUTCD

Section 4D.15 Mounting Height of Signal Faces

04 The bottom of the signal housing (including brackets) of a vehicular signal face that is vertically arranged and not located over a roadway:

    Shall be a minimum of 8 feet and a maximum of 19 feet above the sidewalk or, if there is no sidewalk, above the pavement grade at the center of the roadway.
    Shall be a minimum of 4.5 feet and a maximum of 19 feet above the median island grade of a center median island if located on the near side of the intersection.

Section 4E.05 Location and Height of Pedestrian Signal Heads

Standard:
01 Pedestrian signal heads shall be mounted with the bottom of the signal housing including brackets not less than 7 feet or more than 10 feet above sidewalk level, and shall be positioned and adjusted to provide maximum visibility at the beginning of the controlled crosswalk.

02 If pedestrian signal heads are mounted on the same support as vehicular signal heads, there shall be a physical separation between them.

so it is not a violation of MUTCD, 

[jakeroot]

so it is not a violation of MUTCD,

Thanks for looking that up. Seems to be a rather unusual placement. I'm guessing the "physical separation" requirement keeps the two signals from being on the same level too often.

[freebrickproductions]

Want to say I've seen a fair amount of that in Philadelphia when I visited a few years back.