Protected Left Turn Signal vs. Doghouse vs. Yellow Trap

[traffic light guy]

Doghouses all the way for me, they're the easy to understand, easy to adapt. They can direct both thru traffic and guide ongoing turns. Out of the three, doghouses have been around the longest.

[roadman65]

Yet many think you can only turn on a green arrow in some places as I see many stuck behind the stop bar when the light is green and no oncoming traffic.  Heck I saw a guy once at a Flashing Left Arrow not move at all and no opposing traffic and held up a queue of four or five cars ( some even leaning on their horns) and did not figure that one out either.

[jakeroot]

I swear I've seen this thread before, and I pointed out (as I'm about to again) that "yellow trap" is not a signal, it's a...mistake.

My personal preference for left turns is fully permissive, then FYA, then doghouse/tower, then fully protected.

[freebrickproductions]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.
-Need to allow traffic waiting to turn left a protected left in the middle of a phase? FYA signals can do that, though so can protected-only signals (however, protected only signals can't give any permissive lefts). Doghouses can't.
-Need to allow permissive lefts during certain parts of the day when traffic isn't heavy, but protected-only during rush-hour? FYA signals can do that. Doghouses and protected-only signals can't.
-Need to have an other-wise permissive left turn signal go red when a crosswalk is showing a walk and/or clearance indication? FYA signals can do that. Doghouses and protected-only signals can't.

Really, the main issue that I can think of with an FYA is understandability on the part of the drivers, which is why an education campaign for drivers on the signal via the local media is important.

[traffic light guy]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.
-Need to allow traffic waiting to turn left a protected left in the middle of a phase? FYA signals can do that, though so can protected-only signals (however, protected only signals can't give any permissive lefts). Doghouses can't.
-Need to allow permissive lefts during certain parts of the day when traffic isn't heavy, but protected-only during rush-hour? FYA signals can do that. Doghouses and protected-only signals can't.
-Need to have an other-wise permissive left turn signal go red when a crosswalk is showing a walk and/or clearance indication? FYA signals can do that. Doghouses and protected-only signals can't.

Really, the main issue that I can think of with an FYA is understandability on the part of the drivers, which is why an education campaign for drivers on the signal via the local media is important.

Were people confused this way when doghouses were new?

I do agree that the FYA signal increases traffic flow, for some reason, my state still uses Doghouses. PennDOT is a bit behind compared to the rest of the U.S., when it comes to traffic control.

LG-M327

[freebrickproductions]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.
-Need to allow traffic waiting to turn left a protected left in the middle of a phase? FYA signals can do that, though so can protected-only signals (however, protected only signals can't give any permissive lefts). Doghouses can't.
-Need to allow permissive lefts during certain parts of the day when traffic isn't heavy, but protected-only during rush-hour? FYA signals can do that. Doghouses and protected-only signals can't.
-Need to have an other-wise permissive left turn signal go red when a crosswalk is showing a walk and/or clearance indication? FYA signals can do that. Doghouses and protected-only signals can't.

Really, the main issue that I can think of with an FYA is understandability on the part of the drivers, which is why an education campaign for drivers on the signal via the local media is important.

Were people confused this way when doghouses were new?

I do agree that the FYA signal increases traffic flow, for some reason, my state still uses Doghouses. PennDOT is a bit behind compared to the rest of the U.S., when it comes to traffic control.

LG-M327

Maybe? I think the concept of "Left Turn Yield on Green" had already been around for a while at that point though, so people got used to them rather quickly.

[traffic light guy]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

[jeffandnicole]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

Every state would need to introduce new laws to permit a white colored light, and how to proceed based on the color of the light.

Every state already has laws in place for what to do for a red, yellow and green light.

[cl94]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

Every state would need to introduce new laws to permit a white colored light, and how to proceed based on the color of the light.

Every state already has laws in place for what to do for a red, yellow and green light.

Even then, at least one state had to change laws for the FYA. New York did not allow flashing arrows until NY V&T Law was changed to permit flashing yellow and red arrows when the state adopted the 2009 MUTCD. Several protected-only left turn signals in Regions 3 (Syracuse) and 8 (Hudson Valley) had a fourth section (red ball) that was not used in normal operation, but allowed for flash mode to happen without that signal head going dark.

[jeffandnicole]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

Every state would need to introduce new laws to permit a white colored light, and how to proceed based on the color of the light.

Every state already has laws in place for what to do for a red, yellow and green light.

Even then, at least one state had to change laws for the FYA. New York did not allow flashing arrows until NY V&T Law was changed to permit flashing yellow and red arrows when the state adopted the 2009 MUTCD. Several protected-only left turn signals in Regions 3 (Syracuse) and 8 (Hudson Valley) had a fourth section (red ball) that was not used in normal operation, but allowed for flash mode to happen without that signal head going dark.

NJ's laws don't reflect on all the new technologies and traffic light variations.  Apparently just basic definitions of red, yellow and green lights was good enough, with an additional point made about green arrows.  Other color arrows aren't mentioned.  I've often referred to NJ's use of right red arrows, and that there's always a 'No Turn On Red' sign next to it.  This is probably the reason why, as there's no standard definition for a red arrow in the state.

[jakeroot]

^^
Yeah, same in Washington. I'm not aware of any mention of "flashing yellow arrow" in our Revised Code book. The signals seem to be given their meaning by supplementary signage, which almost all FYAs have.

[UCFKnights]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

Plus the flashing yellow signal (whether an arrow or a ball) has a standardized meaning that the FYA signals are consistent with: use caution and follow the normal ROW rules as if you were not controlled by a signal.

[spooky]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.

Doghouses can do that. Also that's called a yellow trap and you shouldn't do it with doghouses or FYAs.

-Need to allow traffic waiting to turn left a protected left in the middle of a phase? FYA signals can do that, though so can protected-only signals (however, protected only signals can't give any permissive lefts). Doghouses can't.

No signal head is going to change indications "in the middle of a phase". This would require a phase change which could be used to control and/or change indications on any type of left turn signal.

-Need to allow permissive lefts during certain parts of the day when traffic isn't heavy, but protected-only during rush-hour? FYA signals can do that. Doghouses and protected-only signals can't.

A doghouse or a FYA could do this. Yes, you are correct that a protected-only signal can't do permissive phasing.

-Need to have an other-wise permissive left turn signal go red when a crosswalk is showing a walk and/or clearance indication? FYA signals can do that. Doghouses and protected-only signals can't.

This is the only one that a doghouse can't do. A protected-only signal can do this.

Really, the main issue that I can think of with an FYA is understandability on the part of the drivers, which is why an education campaign for drivers on the signal via the local media is important.

This I agree with. The rest of your points are relatively unfounded.

[Skye]

I hate protected ones.  Florence and Erlanger, KY seem to have a lot of those.  The worst ones are when they don't automatically change each cycle, but have to be triggered in time.

[jakeroot]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.

Doghouses can do that. Also that's called a yellow trap and you shouldn't do it with doghouses or FYAs.

-Need to allow traffic waiting to turn left a protected left in the middle of a phase? FYA signals can do that, though so can protected-only signals (however, protected only signals can't give any permissive lefts). Doghouses can't.

No signal head is going to change indications "in the middle of a phase". This would require a phase change which could be used to control and/or change indications on any type of left turn signal.

FYA's can control each approach separately. A default phase could be modified to allow a sudden heavy stream of left turning traffic a random green arrow, assuming no approaching traffic from the side street. Can't do that with a doghouse without visors...

-Need to allow permissive lefts during certain parts of the day when traffic isn't heavy, but protected-only during rush-hour? FYA signals can do that. Doghouses and protected-only signals can't.

A doghouse or a FYA could do this. Yes, you are correct that a protected-only signal can't do permissive phasing.

Doghouse can't without visors (aka Dallas Phasing), which is no longer permitted. So no, doghouses cannot do this anymore.

Really, the main issue that I can think of with an FYA is understandability on the part of the drivers, which is why an education campaign for drivers on the signal via the local media is important.

This I agree with. The rest of your points are relatively unfounded.

Can a doghouse do anything it wants? Sure, if you want a bunch of crashes! (Or you want to use Dallas phasing, which you can't anymore). The FYA was invented to solve the shortcomings of the doghouse, which were its inability to operate correctly at lead/lag permissive lefts, and inability to operate along a time-of-day schedule. A doghouse cannot do either of these without circumventing the MUTCD.

[Pink Jazz]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

White is the color for mass transit-related signals such as for light rail or bus rapid transit.  Perhaps blue, purple, or pink could be options.

[lepidopteran]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

White is the color for mass transit-related signals such as for light rail or bus rapid transit.  Perhaps blue, purple, or pink could be options.

Also pedestrian WALK signals, whether text or "man".  Though I used to see green WALK signals often, and who remembers NYC in the 70's when you could find either green OR white?  There are/were even some mutant blue WALK lights around.

In railroad signals, white light indications are referred to as "lunar white".

[Big John]

^^ MUTCD used to call the pedestrian walk signal "lunar white" but now reads just "white".

[paulthemapguy]

^^ MUTCD used to call the pedestrian walk signal "lunar white" but now reads just "white".

That might be due to the slight change in color brought on by the advent of LEDs.

[freebrickproductions]

IMHO, the FYA signal is objectively better than the doghouse and a protected-only left turn signal, as FYA signals allow for more flexible intersection programming.
For example:
-Need to give both directions permissive lefts, but one protected left at the beginning and one protected left at the end? FYA signals can do that. Doghouses can't, nor can protected only signals.

Doghouses can do that. Also that's called a yellow trap and you shouldn't do it with doghouses or FYAs.

Actually, a FYA can continue to give a permissive left indication while the other direction gets a protected left. Huntsville has an intersection with this set-up at it, where one direction gets a leading left, and the other has a lagging left. The direction without a protected left gets a permissive left while through traffic has a red indication.

[Zmapper]

One feature that I wish transportation departments would do is set flashing yellow arrows to display 'red' when the parallel walk signal is active. While drivers do technically have to yield to pedestrians when turning, even with a 'yellow' arrow displayed, setting traffic signals to protected-only when the pedestrian crosswalk is in use would decrease the chance of increasingly-deadly ped v car crashes.

[Revive 755]

Instead of using a flashing yellow arrow, why not create a new signal color. Perhaps a white arrow

Every state would need to introduce new laws to permit a white colored light, and how to proceed based on the color of the light.

Every state already has laws in place for what to do for a red, yellow and green light.

I know Illinois modified the state statutes for flashing yellow arrows so there were probably a few other states that had to do this.

If it had not been used on the light rail transit signals, white may have been a good idea since it is allowed for LEDs in the border of yield signs.

One feature that I wish transportation departments would do is set flashing yellow arrows to display 'red' when the parallel walk signal is active. While drivers do technically have to yield to pedestrians when turning, even with a 'yellow' arrow displayed, setting traffic signals to protected-only when the pedestrian crosswalk is in use would decrease the chance of increasingly-deadly ped v car crashes.

Considering the number of pedestrians that do not wait for the walk indication and cross when there is a gap (sometimes not sufficient for them to cross), so the walk signal needlessly delays the cycling of the signal  . . .

[jakeroot]

One feature that I wish transportation departments would do is set flashing yellow arrows to display 'red' when the parallel walk signal is active. While drivers do technically have to yield to pedestrians when turning, even with a 'yellow' arrow displayed, setting traffic signals to protected-only when the pedestrian crosswalk is in use would decrease the chance of increasingly-deadly ped v car crashes.

This is extremely common in western Washington. The entirety of Pierce County, along with the cities of Puyallup, Bellevue, and a few others, use protected only phasing when the walk cycle is on. Before I moved recently, I had one of these intersections only about 2 blocks from my house. While the intentions are good, in practice, most pedestrians just cross when there is ample opportunity, and there is hardly ever enough pedestrians for the entire phase needing a red arrow. Bellevue, Washington has done research on the topic, but I can't remember if the research was conclusive or not.

[Pink Jazz]

^^ MUTCD used to call the pedestrian walk signal "lunar white" but now reads just "white".

That might be due to the slight change in color brought on by the advent of LEDs.

I don't think Lunar White was ever specifically required for incandescent pedestrian signals.  It was in use by many DOTs, but was never specifically required.  I do recall seeing some pedestrian signals that are the normal incandescent white.  Once LED pedestrian signals became available, the Lunar White hue became the norm since Warm White LEDs weren't available until much later.

[riiga]

Fully protected left turns, they're safer than any of the alternatives. The Vienna Convention also doesn't allow FYA or similar American solutions.

Regarding permissive lefts, are there any scenarios where the throughput is significantly higher than using a protected turn?