Alternatives to the flashing yellow arrow

[wisvishr0]

what's wrong with this?

If the intersection is too small, there could be a conflict with protected left turns from the opposite direction.

But I guess in retrospect it's not such a huge deal.

[roadfro]

Still, I prefer a flashing red arrow to a flashing yellow arrow, because it'll make sure people don't wait in the middle of the intersection before proceeding. It'll limit the number of people who nudge forward into the intersection before turning -- with a red arrow, your first instinct is to stay behind the stop line until you're clear, rather  than waiting in the middle.

The flashing red would require the driver to make a full stop, even if there is no oncoming traffic, prior to making the permissive left turn. Using the flashing yellow does not require a full stop.

[roadfro]

The FYA also allows for Dallas phasing as the green balls no longer permitted for the left turn lane unless all through lanes in that direction are also displaying green.  It also brings that situation to other areas that never allowed a non-protected left turn where the adjacent through traffic had a red.

what is the difference between these two?  I thought the definition of Dallas phasing was "red for the mainline, permissive green for left-turning traffic"?

Dallas Phasing was developed to allow for lead/lag protected left turns phasing at locations with doghouse displays. The lead/lag protected left allows for better two-way signal timing progression along an arterial, while keeping permitted lefts during the non-permitted portion of the cycle can allow increased throughput during peak hours. However, the lagging left can induce yellow trap on the leading side. Dallas phasing incorporated louvered circular green and yellow displays in the doghouse that were tied to the oncoming through traffic instead of the adjacent, so that the permitted left turn could be made while adjacent through traffic was stopped.

FYAs can run Dallas Phasing. The concept is exactly the same, but it's the FYA that is tied to the opposing through green instead of the circular green. No louvers required, since the arrows don't get mistaken for adjacent through indications.

[vdeane]

Still, I prefer a flashing red arrow to a flashing yellow arrow, because it'll make sure people don't wait in the middle of the intersection before proceeding. It'll limit the number of people who nudge forward into the intersection before turning -- with a red arrow, your first instinct is to stay behind the stop line until you're clear, rather  than waiting in the middle.

Around here, the lead car is supposed to wait in the intersection until there's a gap in traffic or the light turns red.  I get quite annoyed if they don't (especially if there isn't a left turn lane and I therefore don't have room to drive around them).

[jakeroot]

Still, I prefer a flashing red arrow to a flashing yellow arrow, because it'll make sure people don't wait in the middle of the intersection before proceeding. It'll limit the number of people who nudge forward into the intersection before turning -- with a red arrow, your first instinct is to stay behind the stop line until you're clear, rather  than waiting in the middle.

Around here, the lead car is supposed to wait in the intersection until there's a gap in traffic or the light turns red.  I get quite annoyed if they don't (especially if there isn't a left turn lane and I therefore don't have room to drive around them).

Washington State law doesn't really specifiy where you should wait, mostly it ends with "don't block traffic". But in BC, there's a law that states those in intersections (who entered on green) have priority regardless of present signal color. This allows those waiting to turn left to complete their turn without worrying whether they will be honked at/cited/etc.

[The High Plains Traveler]

The FYA also allows for Dallas phasing as the green balls no longer permitted for the left turn lane unless all through lanes in that direction are also displaying green.  It also brings that situation to other areas that never allowed a non-protected left turn where the adjacent through traffic had a red.

what is the difference between these two?  I thought the definition of Dallas phasing was "red for the mainline, permissive green for left-turning traffic"?

FYAs can run Dallas Phasing. The concept is exactly the same, but it's the FYA that is tied to the opposing through green instead of the circular green. No louvers required, since the arrows don't get mistaken for adjacent through indications.

That is one of the only two reasons I would have a FYA: added permissive left turn time when the through indication is red due to oncoming protected left turn. The other is to allow protected-only left turn cycles during heavy traffic periods, and protected-permissive left turns during other times. Most of the FYA signals in my area do one or both, but there are also a few T intersections (thus no oncoming protected left) where the doghouse has been replaced by the FYA with no increase in functionality.

[cl94]

Still, I prefer a flashing red arrow to a flashing yellow arrow, because it'll make sure people don't wait in the middle of the intersection before proceeding. It'll limit the number of people who nudge forward into the intersection before turning -- with a red arrow, your first instinct is to stay behind the stop line until you're clear, rather  than waiting in the middle.

Around here, the lead car is supposed to wait in the intersection until there's a gap in traffic or the light turns red.  I get quite annoyed if they don't (especially if there isn't a left turn lane and I therefore don't have room to drive around them).

Washington State law doesn't really specifiy where you should wait, mostly it ends with "don't block traffic". But in BC, there's a law that states those in intersections (who entered on green) have priority regardless of present signal color. This allows those waiting to turn left to complete their turn without worrying whether they will be honked at/cited/etc.

That's also the law in New York. Any vehicle/pedestrian inside the intersection that entered on a green has priority if their signal turns red, pedestrians over vehicles. I'll add that, while officially illegal, one will rarely get a ticket around here for using the shoulder to get around a turning vehicle in an intersection unless there is a sign specifically telling one not to. NY really only cares about those who run red lights, make illegal turns on red, or block the box.

[jakeroot]

Still, I prefer a flashing red arrow to a flashing yellow arrow, because it'll make sure people don't wait in the middle of the intersection before proceeding. It'll limit the number of people who nudge forward into the intersection before turning -- with a red arrow, your first instinct is to stay behind the stop line until you're clear, rather  than waiting in the middle.

Around here, the lead car is supposed to wait in the intersection until there's a gap in traffic or the light turns red.  I get quite annoyed if they don't (especially if there isn't a left turn lane and I therefore don't have room to drive around them).

Washington State law doesn't really specifiy where you should wait, mostly it ends with "don't block traffic". But in BC, there's a law that states those in intersections (who entered on green) have priority regardless of present signal color. This allows those waiting to turn left to complete their turn without worrying whether they will be honked at/cited/etc.

That's also the law in New York. Any vehicle/pedestrian inside the intersection that entered on a green has priority if their signal turns red, pedestrians over vehicles. I'll add that, while officially illegal, one will rarely get a ticket around here for using the shoulder to get around a turning vehicle in an intersection unless there is a sign specifically telling one not to. NY really only cares about those who run red lights, make illegal turns on red, or block the box.

That reminds me of one of my favorite laws in Washington:

The driver of a vehicle may overtake and pass upon the right of another vehicle only under the following conditions:

     (b) Upon a roadway with unobstructed pavement of sufficient width for two or more lines of vehicles moving lawfully in the direction being traveled by the overtaking vehicle.

[mrsman]

A flashing yellow has always meant slow down, proceed with caution; it does not give you the right-of-way.

If you're at a four-way intersection, and you have a flashing yellow (ball), doesn't that mean cross traffic has a flashing red, and you have the right-of-way?

Except if you're making a left turn facing the flashing yellow. Between the main street and the cross street, yes, you have the right-of-way, but not against oncoming traffic, nor a pedestrian crossing the road.

Alright, so hear me out here....

If you're facing a solid green ball, you have the right of way going straight.
If you're facing a solid green arrow, you have the right of way turning left.
If you're facing a flashing yellow ball, you have the right of way going straight.
If you're facing a flashing yellow arrow, you don't have the right of way???

(Just to be clear, I know exactly what a FYA means.  I'm just playing devil's advocate, saying there's not no reason for confusion.  It's exactly the same as turning right on red on a red arrow.  If you have knowledge of local laws that might border on esoteric, you're fine.  But it could be a lot simpler.)

You are right, which is why it would make more sense in some way to have flashing green ball replace flashing yellow ball.

Flashing red: stop, then proceed.  Equivalent to a stop sign.  Cross-traffic has right of way, except in an all-way stop, where it's shared right of way.

Flashing green:  Traffic has right of way, but cross-traffic may proceed anyway so give slight caution.  Equivalent to the uncontrolled part of a 4-way intersection where only the cross street has a stop sign.  Kind of the way a flashing yellow is used now.

Flashing yellow:  Equivalent to a yield sign.  Other traffic may have the right of way, but you don't need to stop if the way is clear.  [what FYA is supposed to mean]

But of course, the current meaning of flashing yellow is so ingrained, that it would not be wise to change it now.  I guess the flashing yellow just has to be learned.

[wisvishr0]

You are right, which is why it would make more sense in some way to have flashing green ball replace flashing yellow ball.

Flashing red: stop, then proceed.  Equivalent to a stop sign.  Cross-traffic has right of way, except in an all-way stop, where it's shared right of way.

Flashing green:  Traffic has right of way, but cross-traffic may proceed anyway so give slight caution.  Equivalent to the uncontrolled part of a 4-way intersection where only the cross street has a stop sign.  Kind of the way a flashing yellow is used now.

Flashing yellow:  Equivalent to a yield sign.  Other traffic may have the right of way, but you don't need to stop if the way is clear.  [what FYA is supposed to mean]

But of course, the current meaning of flashing yellow is so ingrained, that it would not be wise to change it now.  I guess the flashing yellow just has to be learned.

I completely, totally, fully agree with you. I was about to suggest that myself! I think it makes sense: green means you have the right of way, yellow means you don't, red means you have to stop and either yield, or  take turns. It makes sense!

[agentsteel53]

flashing yellow ball seems to be superfluous from a regulatory perspective: "you have right of way all the time, or at least until this bulb burns out.  proceed with caution, because our licensing system doesn't weed out the morons."

it seems to me that it's the equivalent of a flashing yellow ball on top of a curve advisory yellow-diamond sign or something similar.  just a heads-up that things may get interesting.

[mrsman]

flashing yellow ball seems to be superfluous from a regulatory perspective: "you have right of way all the time, or at least until this bulb burns out.  proceed with caution, because our licensing system doesn't weed out the morons."

it seems to me that it's the equivalent of a flashing yellow ball on top of a curve advisory yellow-diamond sign or something similar.  just a heads-up that things may get interesting.

But you see, sometimes proceed with caution is absolutely necessary.  It is very common in many areas that they turn traffic lights to flash mode overnight.  They want to convert a traffic controlled intersection into a 4-way intersection where only the cross street has a stop sign.  Simply turning off the light is treated in most jurisdictions as an all-way stop.  They need some indication that the main street can go and the side street has a stop sign and they needed it to be a fairly straight forward way of accomplishing it.  So they created the flashing yellow / flashing red sequence.  This can be programmed in most controllers to happen at a fixed time, or it can be programmed over multiple intersections from central traffic control.  The alternative would be to turn off the light and have a foldable stop sign that would be put in place on the side street, but that would require traffic personnel personally going to each intersection to unfold the stop sign. 

[agentsteel53]

But you see, sometimes proceed with caution is absolutely necessary.  It is very common in many areas that they turn traffic lights to flash mode overnight.  They want to convert a traffic controlled intersection into a 4-way intersection where only the cross street has a stop sign.  Simply turning off the light is treated in most jurisdictions as an all-way stop.  They need some indication that the main street can go and the side street has a stop sign and they needed it to be a fairly straight forward way of accomplishing it.  So they created the flashing yellow / flashing red sequence.  This can be programmed in most controllers to happen at a fixed time, or it can be programmed over multiple intersections from central traffic control.  The alternative would be to turn off the light and have a foldable stop sign that would be put in place on the side street, but that would require traffic personnel personally going to each intersection to unfold the stop sign.

I'd advocate changing it to flashing green.  yellow is used for caution, which should not be needed in strictly stated doses at very many intersections at night. 

the problem of the inert traffic light is a serious one.  I always wonder how people can discern which non-indicating traffic lights mean "four-way stop" and which mean "bomb on through".  must be a quirk of each locality.

[roadfro]

Flashing green:  Traffic has right of way, but cross-traffic may proceed anyway so give slight caution.  Equivalent to the uncontrolled part of a 4-way intersection where only the cross street has a stop sign.  Kind of the way a flashing yellow is used now.

Flashing yellow:  Equivalent to a yield sign.  Other traffic may have the right of way, but you don't need to stop if the way is clear.  [what FYA is supposed to mean]

I'm kind of confused by what you mean with the flashing green. Are you saying use a flashing green instead of flashing yellow, such as in red/yellow flash mode? I think that might be a bit more confusing...seeing side street cars passing through a flashing green might violate driver expectancy. Flashing yellow covers this just fine, IMO.

BTW: A 4-way intersection with stop signs on a side street is still a controlled intersection (the stop signs provide the control). An uncontrolled intersection is one with no signals or signs controlling entry on all approaches--usually these are found in residential areas only.

[mrsman]

Flashing green:  Traffic has right of way, but cross-traffic may proceed anyway so give slight caution.  Equivalent to the uncontrolled part of a 4-way intersection where only the cross street has a stop sign.  Kind of the way a flashing yellow is used now.

Flashing yellow:  Equivalent to a yield sign.  Other traffic may have the right of way, but you don't need to stop if the way is clear.  [what FYA is supposed to mean]

I'm kind of confused by what you mean with the flashing green. Are you saying use a flashing green instead of flashing yellow, such as in red/yellow flash mode? I think that might be a bit more confusing...seeing side street cars passing through a flashing green might violate driver expectancy. Flashing yellow covers this just fine, IMO.

BTW: A 4-way intersection with stop signs on a side street is still a controlled intersection (the stop signs provide the control). An uncontrolled intersection is one with no signals or signs controlling entry on all approaches--usually these are found in residential areas only.

If you go back to my original post, I concluded that a change to allow a flashing green would not be wise at this point because the meaning of flashing yellow is already ingrained.  But the point that I was trying to make was that if there were a separate signal indication for yield without stopping, the FYA would be more intuitive. 

I'm not aware that people are really confusing the FYA with the possibility that left turners actually have the right of way when the FYA is displayed.  I think the biggest problem is that the FYA is ignored and that the "yellow trap" problem is not really resolved.  Left turners will see the FYA but they will also see that  adjacent traffic gets a yellow ball and they would assume that both adjacent and opposing traffic sees the yellow ball (and thus will soon see a red ball).  This is ingrained in most drivers and is dangerously incorrect in a FYA controlled lead-lag intersection.

I think that a protected/permissive lagging left is dangerous and leads to a yellow trap unless the opposing left is: 1) also lagging at the same time, 2) prohibited by law, or 3) protected only leading left (red arrow).  The signal indication is irrelevant.

And if we don't need to incorporate a lead-lag protected/permitted left, we don't need a FYA when the doghouse signal works just fine.

[tradephoric]

The flashing red would require the driver to make a full stop, even if there is no oncoming traffic, prior to making the permissive left turn. Using the flashing yellow does not require a full stop.

Yes.  The flashing red ball present at permissive left turns in Michigan technically requires drivers to come to a complete stop.  In reality, the law isn't enforced by Michigan police so drivers don't come to a complete stop when there is no oncoming traffic. 

Yes.  The FYA technically eliminates the "yellow trap" .  In reality, drivers waiting at a permissive left turn who see the adjacent through lane turn yellow automatically assume that the opposing through lane is changing yellow with it (leading to a "perceived yellow trap" ).  I believe many agencies downplay the potential dangers of the "perceived yellow trap"  because they have been assured that the FYA solves the "yellow trap"  problem (which technically it does).   Now, road agencies have free reign to install as many "perceived yellow trap"  situations at FYA intersections as they would like.

At some point, reality trumps theory.  The reality is the total number of injury accidents have increased by 30% at new FYA installs throughout SE Michigan.  The "perceived yellow trap" , which was rarely seen under Michigan's old style flashing red ball, is becoming commonplace at FYA intersections throughout the region.  Also, it may have been a mistake to incorporate a flashing yellow arrow as opposed to a flashing red arrow.  A segment of the driving population approaching a flashing yellow arrow will wrongfully assume that they have the right of way (since they equate yellow to mean "Proceed with caution"  or even just "Proceed" ).  From a safety standpoint, the FYA has failed in SE Michigan.  That's the reality.

[jakeroot]

At some point, reality trumps theory.  The reality is the total number of injury accidents have increased by 30% at new FYA installs throughout SE Michigan.  The "perceived yellow trap" , which was rarely seen under Michigan's old style flashing red ball, is becoming commonplace at FYA intersections throughout the region.  Also, it may have been a mistake to incorporate a flashing yellow arrow as opposed to a flashing red arrow.  A segment of the driving population approaching a flashing yellow arrow will wrongfully assume that they have the right of way (since they equate yellow to mean "Proceed with caution"  or even just "Proceed" ).  From a safety standpoint, the FYA has failed in SE Michigan.  That's the reality.

Of course accidents went up. We've allowed more traffic to proceed through an intersection in a given window of time, and thus the intersection throughput has been increased, and thus the amount accidents increased. I think it's well established that busier intersections have more accidents (that's why we invented grade-separated interchanges).

That reminds me of when Washington privatized liquor sales. People got all up in arms because liquor theft went up . . . well, of course it did! There's more alcohol!

[tradephoric]

^I'm not buying it.  Most of the FYA installs in SE Michigan were around 2008-2010 (the after crash data was looking at 3 years immediately following the great recession).    Traffic volumes were down during this period.  There is no evidence that traffic volumes increased by 30% to explain away the 30% increase in total injury accidents at the FYA intersections.  Regardless, the FYA wouldn't be able to increase intersection capacity by 30%.  With the FYA you still have left turn phases which prevents any significant gains in capacity.   

[jakeroot]

^I'm not buying it.  Most of the FYA installs in SE Michigan were around 2008-2010 (the after crash data was looking at 3 years immediately following the great recession).    Traffic volumes were down during this period.  There is no evidence that traffic volumes increased by 30% to explain away the 30% increase in total injury accidents at the FYA intersections.  Regardless, the FYA wouldn't be able to increase intersection capacity by 30%.  With the FYA you still have left turn phases which prevents any significant gains in capacity.   

Fair enough. My second problem then is the stats themselves. Why are three years worth of collisions crammed into one table? There were 758 injury collisions in the three years after the FYA install, versus 579 in the three years prior. When you have three years of stats in one whole, it's not possible to tell if collisions are actually dropping off or not. For example (and this is purely an example based on zero real-world evidence), what if there were 300 collisions in the first year after the FYA install, then only 200, and then only 158? That would actually show the FYA as working, but again, there's no way to tell.

Is there a year-by-year study anywhere?

[vdeane]

With the FYA you still have left turn phases which prevents any significant gains in capacity.   

But traffic is also able to turn left outside of the left turn phases, so in intersections that went from protected-only to FYI, the volume of turning vehicles increased.

[Brandon]

With the FYA you still have left turn phases which prevents any significant gains in capacity.   

But traffic is also able to turn left outside of the left turn phases, so in intersections that went from protected-only to FYI, the volume of turning vehicles increased.

No they did not.  These intersections were protected/permissive before.  All they did was to go from the flashing red ball to the flashing yellow arrow.  Thus, there was zero gain in volume.

[jakeroot]

With the FYA you still have left turn phases which prevents any significant gains in capacity.   

But traffic is also able to turn left outside of the left turn phases, so in intersections that went from protected-only to FYI, the volume of turning vehicles increased.

No they did not.  These intersections were protected/permissive before.  All they did was to go from the flashing red ball to the flashing yellow arrow.  Thus, there was zero gain in volume.

Do you honestly believe that making traffic stop before turning has the same capacity as making traffic simply yield?

[cl94]

With the FYA you still have left turn phases which prevents any significant gains in capacity.   

But traffic is also able to turn left outside of the left turn phases, so in intersections that went from protected-only to FYI, the volume of turning vehicles increased.

No they did not.  These intersections were protected/permissive before.  All they did was to go from the flashing red ball to the flashing yellow arrow.  Thus, there was zero gain in volume.

Do you honestly believe that making traffic stop before turning has the same capacity as making traffic simply yield?

If opposing traffic makes it so one has to stop to yield for the majority of a cycle, it's pretty close. But in such a case, I'd just use a protected-only with ITS shortening green times if demand isn't there.

[jakeroot]

With the FYA you still have left turn phases which prevents any significant gains in capacity.   

But traffic is also able to turn left outside of the left turn phases, so in intersections that went from protected-only to FYI, the volume of turning vehicles increased.

No they did not.  These intersections were protected/permissive before.  All they did was to go from the flashing red ball to the flashing yellow arrow.  Thus, there was zero gain in volume.

Do you honestly believe that making traffic stop before turning has the same capacity as making traffic simply yield?

If opposing traffic makes it so one has to stop to yield for the majority of a cycle, it's pretty close. But in such a case, I'd just use a protected-only with ITS shortening green times if demand isn't there.

Well yeah, if there's opposing traffic it doesn't matter. But consider all the times when there isn't any opposing traffic. Stopping would absolutely impede the regular, consistent flow of traffic.

[tradephoric]

Fair enough. My second problem then is the stats themselves. Why are three years worth of collisions crammed into one table? There were 758 injury collisions in the three years after the FYA install, versus 579 in the three years prior. When you have three years of stats in one whole, it's not possible to tell if collisions are actually dropping off or not. For example (and this is purely an example based on zero real-world evidence), what if there were 300 collisions in the first year after the FYA install, then only 200, and then only 158? That would actually show the FYA as working, but again, there's no way to tell.

Is there a year-by-year study anywhere?

The Southeast Michigan Counsel of Governments (SEMCOG) compiles crash data on a yearly basis for every major intersection in SE Michigan.  Here is a link to the crash data for Macomb County:

http://www.semcog.org/data/apps/highcrash.report.cfm?mcd=3999&numReturn=100&ftype=0

Using this public data,  you can look back at over 10 years of crash data for any intersection of interest.  I broke the numbers down by year in the chart below per your request.