One weird Flashing yellow arrow

[Amtrakprod]

Went biking and found this strange signal, any opinions?
Link to YouTube video: https://youtu.be/kNvR_sIJc_E
If anyone wants to see what used to be there and the intersection layout, the intersection is: Bedford St opp Hartwell Ave, Lexington, MA 02420 .


iPhone

[paulthemapguy]

^Yes that signal phase sequence is very strange.  Is a yellow ball into a FYA even permissible? 
Whoever was in charge decided to make the intersection a split-phase, but in a way that allows pedestrian crossings.  That's hard to pull off when the expressway offramp mostly will want to turn right or left.  Every approach to the intersection is going to want to access the approach on the left of the screen...so when do you allow pedestrians to cross there?
Also, the approach moving into the screen can't go straight, so how do you set up the indications to alert motorists to the fact that they absolutely must turn?
There's a lot of interesting challenges at this intersection.  A strange scenario begets a strange signal.  I probably would have done it a bit differently.

Also...WHY is there a "left turn yield on green" sign when there's a GREEN ARROW INDICATION?  No.  That is just not how that works.  I can say without a doubt that was just done incorrectly.  If you want people to yield on the left turn, they should have made the FYA the most permissive indication, doing away with the green arrow altogether.

[roadfro]

^Yes that signal phase sequence is very strange.  Is a yellow ball into a FYA even permissible? 
Whoever was in charge decided to make the intersection a split-phase, but in a way that allows pedestrian crossings.  That's hard to pull off when the expressway offramp mostly will want to turn right or left.  Every approach to the intersection is going to want to access the approach on the left of the screen...so when do you allow pedestrians to cross there?
Also, the approach moving into the screen can't go straight, so how do you set up the indications to alert motorists to the fact that they absolutely must turn?
There's a lot of interesting challenges at this intersection.  A strange scenario begets a strange signal.  I probably would have done it a bit differently.

Also...WHY is there a "left turn yield on green" sign when there's a GREEN ARROW INDICATION?  No.  That is just not how that works.  I can say without a doubt that was just done incorrectly.  If you want people to yield on the left turn, they should have made the FYA the most permissive indication, doing away with the green arrow altogether.

The whole odd signal signal setup is not necessary as implemented, as the intersection isn't really that complicated. here's the Google Map

This is really a T-intersection with a jughandle (with jughandle traffic seen opposite of the camera view in the video). The camera is viewing from the stem of the "T". The stem has a right turn island, so the only traffic subjected to these signals are a left turn. There is no reason a standard all arrow FYA display couldn't have been used here.


The most likely reason for the "left turn yield on green" sign is that it is a remnant from when there was a doghouse signal on that pole that wasn't removed when the signal was upgraded (you can see the doghouse in Street View).

[paulthemapguy]

The whole odd signal signal setup is not necessary as implemented, as the intersection isn't really that complicated. here's the Google Map

This is really a T-intersection with a jughandle (with jughandle traffic seen opposite of the camera view in the video). The camera is viewing from the stem of the "T". The stem has a right turn island, so the only traffic subjected to these signals are a left turn. There is no reason a standard all arrow FYA display couldn't have been used here.

Ok, so it's not an expressway offramp, but it's an offramp.  But, assuming the camera faces north, let's say the crosswalk across the west leg of the intersection is activated.  That's not a situation when you want a solid green left arrow for the northbound approach.  Here in Illinois, if you're at an intersection like this with a crosswalk to the left, the most permissive indication would be a green ball.  You don't want to tell left turners to proceed freely when pedestrians have the ultimate right-of-way.  I would suggest either:
1) a 3-section head with a red, yellow, and FYA indication, or
2) a standard 3-section head with all ball indications

The most likely reason for the "left turn yield on green" sign is that it is a remnant from when there was a doghouse signal on that pole that wasn't removed when the signal was upgraded (you can see the doghouse in Street View).

Okay.  That makes sense.  They ought to remove that sign though lol

[roadfro]

The whole odd signal signal setup is not necessary as implemented, as the intersection isn't really that complicated. here's the Google Map

This is really a T-intersection with a jughandle (with jughandle traffic seen opposite of the camera view in the video). The camera is viewing from the stem of the "T". The stem has a right turn island, so the only traffic subjected to these signals are a left turn. There is no reason a standard all arrow FYA display couldn't have been used here.

Ok, so it's not an expressway offramp, but it's an offramp.  But, assuming the camera faces north, let's say the crosswalk across the west leg of the intersection is activated.  That's not a situation when you want a solid green left arrow for the northbound approach.  Here in Illinois, if you're at an intersection like this with a crosswalk to the left, the most permissive indication would be a green ball.  You don't want to tell left turners to proceed freely when pedestrians have the ultimate right-of-way.  I would suggest either:
1) a 3-section head with a red, yellow, and FYA indication, or
2) a standard 3-section head with all ball indications

Since the intersection appears to run in split phase (or at least it can be based on pedestrian activation), there's still no problem using an all arrow FYA display if the crosswalks run independently.

In the video, the camera operator pushes the button for the east leg crosswalk, and the east leg crosswalk is activated during the northbound green arrow phase–but this does not necessarily mean that the west leg crosswalk was activated at the same time. If a pedestrian had pressed the button for the west leg crosswalk at the same time, their crossing phase would not have been activated until the southbound jughandle traffic had their green–during this time, the northbound traffic had the FYA. Permitted lefts on an FYA across an active crosswalk indication are no different than permitted lefts on a green ball across an active crosswalk–the turning vehicles still have to yield to oncoming traffic and pedestrians legally in the crosswalk.

[Amtrakprod]

^Yes that signal phase sequence is very strange.  Is a yellow ball into a FYA even permissible? 
Whoever was in charge decided to make the intersection a split-phase, but in a way that allows pedestrian crossings.  That's hard to pull off when the expressway offramp mostly will want to turn right or left.  Every approach to the intersection is going to want to access the approach on the left of the screen...so when do you allow pedestrians to cross there?
Also, the approach moving into the screen can't go straight, so how do you set up the indications to alert motorists to the fact that they absolutely must turn?
There's a lot of interesting challenges at this intersection.  A strange scenario begets a strange signal.  I probably would have done it a bit differently.

Also...WHY is there a "left turn yield on green" sign when there's a GREEN ARROW INDICATION?  No.  That is just not how that works.  I can say without a doubt that was just done incorrectly.  If you want people to yield on the left turn, they should have made the FYA the most permissive indication, doing away with the green arrow altogether.

If you watched my video, you would have seen it is a flashing yellow arrow


iPhone

[Amtrakprod]

I'll explain the phase better(btw I was the one who filmed this).

The straight has a green signal until cars are detected or I click the button, then the green arrow would come on if a car was turning left or if someone(like me) clicked the button, then the signal would go yellow, and then start the flashing yellow arrow sequence.


iPhone