Five Section or doghouse signal head for left turns?

[vdeane]

Another simple solution: don't let a turn yellow and any conflicting greens to overlap.

[formulanone]

These five-section lights for left turns were very common in Florida until the 1990s, when many of the intersections were widened, creating twin turning lanes, each with their own 3-section signals. It's also become more common for the intersections to be modified for protected signals on roads with higher traffic counts.

They're still a common enough sight on many four-lane roads, or two-lane roads with heavy traffic.

[M3019C LPS20]

For many years, New York City only used a green arrow indication for protected turn movements. In addition to that, the leading protected turn movement was the ideal sequence used. The amber arrow indication did not appear until perhaps the 1970s there. Even so, the original sequence was still widely used. It eventually disappeared for the most part, and some signalized intersections, as a handful, throughout New York City continue to use it. One that I am aware of exists on Staten Island.

Today, N.Y.C.D.O.T. commonly uses the G.A./A.A. head for a leading protected turn movement (commonly left). Over the years, original sections that only used green arrow indications were connected with additional heads that show amber indications.

Perhaps you could consider the set-up as a "doghouse" of some sorts, but New York City tends to place an ordinary 8" head with a 12-12 head next to it in a cluster.

[Revive 755]

It appears at least western Kentucky uses doghouses.


Regarding the perceived yellow trap when a flashing yellow arrow is used with lead-lag phasing, if there really is a safety issue with this, I would have expected one or more agencies to have noticed it by now.

[dfnva]

The thing I found most interesting about the Charlottesville videos linked above was the weird right-on-red sign on 10th Street at Grady Avenue. Street View with a curb-mounted sign may be seen here. I can't say I've ever seen a sign like that before, including at that intersection (the sign was definitely not there when I attended UVA because I'd remember something like that). The message is straightforward enough, though I wonder if it might be a bit wordy when you see it in person. If I remember, I will have to drive past it when we go to a football game this fall.

(That whole intersection complex was always weird. Going west on Preston Avenue, the light would turn red for traffic turning left onto Grady but stay green to continue straight on Preston. Immediately afterwards the intersection of Preston and 10th had a flashing yellow light that's now gone. So anyone who knew the area would go straight on Preston, hang a left at the flashing yellow, and then go right on red onto Grady. Saved you a long wait at the left-turn light.)

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you–I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

I never knew this was called lead lag, but I've only seen it in VA when one or two directions of a street have double left turn lanes so that there's room for the protected left turn to be completed safely.

Some examples:
* VA-28/Centreville Rd at Liberia Ave. in Manassas
* VA-234/Pr. William Pkwy at SR-674/Wellington Rd in Manassas

There are other intersections that should have this because of near misses --- VA-234-Bus/Sudley Rd and SR-1566/Sudley Manor Dr comes to mind.

[tradephoric]

Regarding the perceived yellow trap when a flashing yellow arrow is used with lead-lag phasing, if there really is a safety issue with this, I would have expected one or more agencies to have noticed it by now.

The Southeast Michigan Counsel of Governors (SEMCOG) collects 10 years of crash data for intersections throughout the region and publishes the data on their website.   Previous to the FYAs, Macomb County used the flashing red ball for permissive left turns.  When you compare the 3 years of before and after crash data, there is a 20% increase in injury accidents at the FYA intersections.  Other counties in the region have seen similar trends of increased injury accidents at FYA intersections.  The safety of FYAs became a hot topic last year when Oakland County Executive L. Brooks Patterson was involved in a serious accident at a FYA in August of 2012.  Patterson nearly died in the accident and his driver, James Cram, was left a quadriplegic.

I have no idea if the increase in injury accidents at FYAs throughout the region is due to the "perceived yellow trap".  It should be noted that this trap can be seen in not just lead-lag, but also in lag-lag where one of the lagging left turns is allowed to skip when no vehicles are being detected.  Most of the FYAs in Macomb County is set up for lag-lag with the left turn phases allowed to skip.

[froggie]

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you–I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

Yes, that sounds like lead-lag, though lead-lag is (almost always) applied to protected-only left situations and not phasing that includes a permitted left.  There is a fair amount of it in both Northern Virginia (I lived right next to one on Route 1/Huntington Ave) and also in Hampton Roads (especially in Virginia Beach).

[1995hoo]

A lot of Charlottesville's left-turn lights always had unusual phasing compared to the rest of Virginia as well. I believe "mtantillo" of this forum once told me (somewhere else) that the phasing is called "lead-lag." Using Emmet Street at Ivy Road as an example: (1) Northbound Emmet gets a green ball to go straight and a green left arrow, southbound Emmet has a red. (2) The green arrow turns off and southbound Emmet gets a green ball but no turn arrow (so both directions are going straight). (3) Northbound Emmet's light turns completely red and southbound Emmet gets the green left-turn arrow along with the green ball. This is highly non-standard pretty much everywhere else I've driven in Virginia (normally both directions get the left arrows at the beginning of the light cycle). I'm not saying it's never used elsewhere in Virginia, mind you–I'm just saying it's remarkably common in Charlottesville compared to everywhere else in the Commonwealth.

Yes, that sounds like lead-lag, though lead-lag is (almost always) applied to protected-only left situations and not phasing that includes a permitted left.  There is a fair amount of it in both Northern Virginia (I lived right next to one on Route 1/Huntington Ave) and also in Hampton Roads (especially in Virginia Beach).

That may be why (as another poster verified) the City of Charlottesville got rid of it at the corner of Emmet and Ivy. That particular intersection also sees a lot of pedestrian and bike traffic, obviously, due to the University being directly adjacent to both streets. So having people encountering a "yellow trap" there is probably all the more dangerous if there's heavy pedestrian traffic that would be put at risk if a turning vehicle were broadsided by a car going 35 mph.

But anyway, regarding it in the rest of Virginia, I believe I acknowledged it's used; my point was just that Charlottesville seemed to have a disproportionate amount of it concentrated in one area compared to the rest of the Commonwealth.

I actually encountered a strange one this morning after dropping of Ms1995hoo at the Van Dorn Metrorail–I looped around on Metro Road to southbound Van Dorn and got a red light just as I approached the stop bar; the northbound side was already green and then their green arrow came on after our red. The reason I say it's strange is that almost every other time I go through there, it's a more conventional cycle with protected left turns for both directions at the leading end of the light cycle. I think I've seen the tail-end green arrow maybe one or two other times (and I've lived in Kingstowne for 11 years, so I use Van Dorn constantly) and there seems to be little rhyme or reason to when it does it. Weird stuff.

[tradephoric]

Here is a list of FYA intersections in Macomb County.  Injury accidents have increased by 30% when comparing the before/after crash data.   All data obtained through SEMCOG:

[Henry]

Although I grew up in a state with 5-section signals (as the OP stated), it seems to me that doghouses are more common in the nation as a whole.

[roadfro]

The FYA effectively eliminates the possibility of the yellow trap but it can still lead to what i call the "perceived yellow trap".   Does anyone think the signal phasing from 1:30 through 1:35 in the video could be confusing to some drivers and lead to a perceived yellow trap?

I don't think this leads to a "perceived yellow trap". One of the features of the FYA display, whether the standard 4-section (as shown) or 3-section variant (with shared FYA & steady green arrow bottom section) is the separation of the FYA and the normal yellow arrow. The visual jump between different signal sections and yellow arrows should be the cue to the left turning driver that they need to make a decision...the through traffic signals should not be a factor.

[jeffandnicole]

But only if they notice the light. If they're already in the intersection waiting for a gap in traffic, it's very easy to not notice a light becoming steady yellow rather than flashing yellow.

[roadfro]

Tradephoric was saying that a quick glance at the signal head might cause one to inadvertently assume a flashing yellow was becoming steady. I assert that if you make a quick glance and note that the yellow arrow has jumped sections, then that's when you'd need to worry--if the yellow is still in the same section as where it was flashing before, there's no need to worry. It's a lot more noticeable that a light has changed sections than it is to switch from flashing to steady in the same signal section. This is why I prefer the 4-section FYA to the 3-section variant.

[Alps]

Tradephoric was saying that a quick glance at the signal head might cause one to inadvertently assume a flashing yellow was becoming steady. I assert that if you make a quick glance and note that the yellow arrow has jumped sections, then that's when you'd need to worry--if the yellow is still in the same section as where it was flashing before, there's no need to worry. It's a lot more noticeable that a light has changed sections than it is to switch from flashing to steady in the same signal section. This is why I prefer the 4-section FYA to the 3-section variant.

Agreed, and that's why the MUTCD shows a separate section for the FYA from the SYA in its signal diagrams.

[Mark68]

Colorado was mostly doghouse (probably as an add-on to the old 12-8-8 signals hanging from overhead wires in places such as Denver), then had some 4-sections and mostly 5-sections that were side-mounted (or center-mounted in the medians). Denver had some interesting ones with the normal 8-8-8 three section signals with two 12-inch signals added to the bottom for the green and yellow turn arrows. Now Aurora is installing the FYA (usually with four sections, some with three), Denver has installed their first two FYAs, and I have not heard of any other ones...yet...in other cities.

[tradephoric]

Tradephoric was saying that a quick glance at the signal head might cause one to inadvertently assume a flashing yellow was becoming steady. I assert that if you make a quick glance and note that the yellow arrow has jumped sections, then that's when you'd need to worry--if the yellow is still in the same section as where it was flashing before, there's no need to worry. It's a lot more noticeable that a light has changed sections than it is to switch from flashing to steady in the same signal section. This is why I prefer the 4-section FYA to the 3-section variant.

Agreed, and that's why the MUTCD shows a separate section for the FYA from the SYA in its signal diagrams.

The Macomb County FYA's are all the 4-section FYA variety yet still have seen a large increase in injury accidents.  A 30% increase in injury accidents at FYA installs is concerning.  At some point the theory goes out the window and the focus should on where the rubber meets the road.  I would love to see before/after safety studies at FYA installs throughout the country to see if the increase in injury accidents at FYAs are more than just a regional phenomenon. 

[Alps]

Tradephoric was saying that a quick glance at the signal head might cause one to inadvertently assume a flashing yellow was becoming steady. I assert that if you make a quick glance and note that the yellow arrow has jumped sections, then that's when you'd need to worry--if the yellow is still in the same section as where it was flashing before, there's no need to worry. It's a lot more noticeable that a light has changed sections than it is to switch from flashing to steady in the same signal section. This is why I prefer the 4-section FYA to the 3-section variant.

Agreed, and that's why the MUTCD shows a separate section for the FYA from the SYA in its signal diagrams.

The Macomb County FYA's are all the 4-section FYA variety yet still have seen a large increase in injury accidents.  A 30% increase in injury accidents at FYA installs is concerning.  At some point the theory goes out the window and the focus should on where the rubber meets the road.  I would love to see before/after safety studies at FYA installs throughout the country to see if the increase in injury accidents at FYAs are more than just a regional phenomenon. 

I hate them, myself. To me, the only application that makes sense is Dallas phasing (lead arrow one direction, lag arrow the other), and even then, states have had success with a flashing red arrow instead. (Hey, Delaware.) Red's safer than yellow.

[froggie]

Oddly enough, as I recall from the FYA testing, it was found that the FYA had better "signal recognition" from drivers than the traditional 5-lens (whether doghouse or vertical).

[tradephoric]

I hate them, myself. To me, the only application that makes sense is Dallas phasing (lead arrow one direction, lag arrow the other), and even then, states have had success with a flashing red arrow instead. (Hey, Delaware.) Red's safer than yellow.

This is what Delaware drivers are taught to do at a flashing red arrow, taken directly from the Delaware Driver Manual:

Flashing red Arrow:  Turns are permitted in the direction of a flashing red arrow after coming to a full stop. The full stop enables drivers to select a safe gap in the main flow of traffic, and then complete the turn without waiting for a green signal. Signal may be followed by a steady red arrow, steady yellow arrow or solid red ball.

While this may be what is taught, i doubt it is practiced by Delaware drivers.  I imagine very few drivers will actually come to a complete stop at a flashing red arrow when there is safe gap in traffic.  Michigan has the same type setup as Delaware (just with a flashing red ball as opposed to a flashing red arrow).  This is what Michigan drivers are taught to do at a flashing red light:

A flashing red light means come to a full stop.  Proceed when the road is clear.

In Michigan, drivers do not come to a complete stop when making a permissive left turn at a flashing red ball (assuming there is a safe gap in traffic).  It's just a rule that isn't followed.  I would say 99% of drivers in Michigan do not come to a complete stop, and that's a conservative estimate.  If a driver does come to a complete stop, they are liable to get honked at and/or rear ended by the vehicle behind them.   

[jeffandnicole]

I hate them, myself. To me, the only application that makes sense is Dallas phasing (lead arrow one direction, lag arrow the other), and even then, states have had success with a flashing red arrow instead. (Hey, Delaware.) Red's safer than yellow.

This is what Delaware drivers are taught to do at a flashing red arrow, taken directly from the Delaware Driver Manual:

Flashing red Arrow:  Turns are permitted in the direction of a flashing red arrow after coming to a full stop. The full stop enables drivers to select a safe gap in the main flow of traffic, and then complete the turn without waiting for a green signal. Signal may be followed by a steady red arrow, steady yellow arrow or solid red ball.

While this may be what is taught, i doubt it is practiced by Delaware drivers.  I imagine very few drivers will actually come to a complete stop at a flashing red arrow when there is safe gap in traffic.  Michigan has the same type setup as Delaware (just with a flashing red ball as opposed to a flashing red arrow)... 

You are pretty much correct. And if they are stopping, they are doing so well beyond the stop line, waiting for a gap in traffic.

Having said that, at least in the New Castle County area, a lot of the flashing left arrows have been eliminated, and now are simply protected left turns.

They also have a few oddball ones, like this example on Rt. 4 in Newark: It's basically a u-turn lane. WB Rt. 4 doesn't have a light whatsoever. The u-turn has a flashing red arrow, and EB Rt. 4 has a regular traffic light.  By zooming out of the street view & looking around, the light's only reasonable purpose is to help serve traffic exiting a residential street that must turn right onto Rt. 4 WB before u-turning onto Rt. 4 EB.  Even then, traffic would come to a regular, signalized intersection if they simply went over one block within that community.

[The High Plains Traveler]

Colorado was mostly doghouse (probably as an add-on to the old 12-8-8 signals hanging from overhead wires in places such as Denver), then had some 4-sections and mostly 5-sections that were side-mounted (or center-mounted in the medians). Denver had some interesting ones with the normal 8-8-8 three section signals with two 12-inch signals added to the bottom for the green and yellow turn arrows. Now Aurora is installing the FYA (usually with four sections, some with three), Denver has installed their first two FYAs, and I have not heard of any other ones...yet...in other cities.

CDOT District 2 (Pueblo/Colorado Springs) uses them extensively. More so than the rest of the state put together.

[roadfro]

The Macomb County FYA's are all the 4-section FYA variety yet still have seen a large increase in injury accidents.  A 30% increase in injury accidents at FYA installs is concerning.  At some point the theory goes out the window and the focus should on where the rubber meets the road.  I would love to see before/after safety studies at FYA installs throughout the country to see if the increase in injury accidents at FYAs are more than just a regional phenomenon. 

You have to look at the type of accidents in totality though. A straight 30% increase in accidents doesn't tell you anything if you don't know the particulars of the accident. Is that increase directly attributable to the new FYA, or are there other factors that come into play? If there's an accompanying change of signal phasing with the FYA installation, that could be a factor. What's the duration of the accident increase--over a year, over three years, over three months? Three years of accident data is typically considered the minimum data period for a statistically significant traffic safety study/comparison. Is the increase in minor injury accidents offset by a reduction in serious injury accidents?

I seem to recall that some of the early adopters of FYAs (possibly somewhere in Oregon) had some before/after studies that showed reduction in accidents after FYAs went in. Don't quote me on that though...

I hate them, myself. To me, the only application that makes sense is Dallas phasing (lead arrow one direction, lag arrow the other), and even then, states have had success with a flashing red arrow instead. (Hey, Delaware.) Red's safer than yellow.

Flashing red requires the full stop though, whereas flashing yellow doesn't. In replacing a circular green, using a flashing red doesn't achieve the same purpose and decreases throughput with the full stop (assuming vehicles actually come to a full stop). That said, FHWA did adopt some provision to use flashing red arrows in the last MUTCD, but that was more meant for permissive turns with safety things that would need a full stop (i.e. sight distance issues).

[Brandon]

^^ However, the flashing red for a left turn is never treated as a complete stop unless opposing traffic is has not cleared.  See Tradephroic's discussion of Michigan above (which I am very familiar with).

[The High Plains Traveler]

^^ However, the flashing red for a left turn is never treated as a complete stop unless opposing traffic is has not cleared.  See Tradephroic's discussion of Michigan above (which I am very familiar with).

Then how would that differ from a flashing yellow arrow? Notwithstanding what Michigan did in the past with its flashing solid red indications, any present-day installations of flashing red arrows are intended to require turning traffic to come to a full stop, for the reasons cited by roadfro above.

[Big John]

Flashing red means come to a full stop before proceeding.  Same as if the intersection was in flash mode, or a stop sign with a flashing red beacon above it.