some red and some green signals for "same direction" on one approach?

[johndoe]

(inspired by the "perpetual green" thread) Let's say you have a diamond interchange plus 1 parclo on-ramp.  If the parclo movement lane continues upstream through the other signal, you could give them the "perpetual green" since the off-ramp left turn doesn't conflict with the parclo move.  But if it's only a single parclo ramp rather than two (A4) you also have to contend with the left-turn onto the diamond ramp. 

How about an example: https://goo.gl/maps/GRZjPP2VFKmCzps96  Let's say the parclo movement is super busy and they want to give it green at the same time as the northbound ramp.  They extend the island to ensure the northbound ramp can't go through.  Then the westbound drivers would see two different sets of 3-section-heads: at times both would be red (EBL), both would be green (WBT), or only the right would be green (NBL). 

Anyone know of any examples like this?  Does MUTCD even allow such a thing (where the "same direction" gets different indications)?

[SkyPesos]

Here's one in my area at SB Reed Hartman Hwy and Kemper Rd. The continuous green light is for the ramp from I-275 EB to Reed Hartman SB.

[jakeroot]

One example near me:

Coal Creek Pkwy @ I-405 / 119 Ave SE

Coal Creek Pkwy, approaching 119 Ave SE, has a right turn lane that is for the second intersection, the 405 northbound onramp. When the left turn signal onto the 405 northbound onramp is green (it is fully protected unlike the other left turn onto southbound 405), the right lane through the intersection at 119 Ave SE remains green, to allow traffic to continue to the ramp and turn on red, whilst traffic coming the other direction has a green indication at both signals. It is quite bizarre, and I cannot readily think of similar situations.

Typical for this area, there is nothing in the way of signage. It is just assumed that, because of the 3M signal, only the relevant traffic will see the green signal. It doesn't seem anyone is confused by the regular signals showing red over the through lanes; I go through this intersection almost daily and I've never seen anyone get it wrong.


Coal Creek Parkway at 405 by Jacob Root, on Flickr

[PurdueBill]

If the onramp to 15 NB didn't line up so perfectly with the offramp from 15 NB, the potential for people going straight through (despite the signs showing a double left, no straight arrow) would be eliminated.  As is, even if left turns from EB to NB had the red while NB to WB had the green, some straggler might go straight to get back on 15 NB and cross paths with WB traffic going for the loop to SB, so probably best to have their red the same as the thru WB even though it seems like extra wait.  If only the geometry were different such that the straight-through look from offramp to onramp weren't there, then green for WB to the loop ramp could be safe while straight through WB is red for the NB offramp to enter.

The closest thing (although not exactly it) locally is at CLE airport where three entry roadways merge together and while there are no turns at that immediate location, there is another intersection close enough that free-flowing would not allow traffic from the left to make it over to the right (or vice-versa), so the merge is signalized with PV heads of course.  https://goo.gl/maps/w3CKJ5GvuT2oX8T17

[johndoe]

So for the parclo I guess it would likely be tricky to have islands block "off-ramp throughs" while still allowing "lefts on".  Maybe it's easier if the "off-ramp" is a little closer to the bridge than the "on-ramp", something like this:


Thanks for the examples.  Jake's is pretty wacky, I'm not sure I get the big benefit.  When this green happens during the opposing left at the next signal, what's the problem with just having all lanes green?  Sure it'll fill up that space but the right lane will also fill as-is since they have to yield to the "lefts on".  If the turn onto the ramp was a free movement with an extra lane (like the LV example) I could see the benefit.  I assume this signal head doesn't go green when 119th does?

[jakeroot]

Thanks for the examples.  Jake's is pretty wacky, I'm not sure I get the big benefit.  When this green happens during the opposing left at the next signal, what's the problem with just having all lanes green?  Sure it'll fill up that space but the right lane will also fill as-is since they have to yield to the "lefts on".  If the turn onto the ramp was a free movement with an extra lane (like the LV example) I could see the benefit.  I assume this signal head doesn't go green when 119th does?

If I had to guess, I think they decided to hold straight-through traffic at the prior stop line because they were worried about blocking issues, which wouldn't really be a big deal for traffic turning into the 405 (as they can simply turn on red).

This signal head is green until 119 Ave SE has their green, and then it goes all red. I think an ideal setup would be a double right turn onto the on-ramp, with the right lane of Coal Creek Parkway continuing through as a continuous green-T, with traffic coming in from 119 Ave SE able to turn right onto the 405 from their own right turn lane. But the on-ramp is only a single lane, so that won't be happening.

[MASTERNC]

There was one for a while in Delaware during a construction project.  Because of bridge work, traffic on SR 141 over I-95 was split.  The right lane alternated traffic with a cloverleaf ramp from I-95, controlled by a signal.  The left lane was separated by channelizers and had continuous green arrows over the lane.

[mrsman]

Here's an example that will allow off-ramp traffic to be continuous, while street traffic is stopped.  The cement island between the two roadways separates the traffic flows, so there is no need for a continuous green here:

https://www.google.com/maps/@39.0555625,-77.1497583,3a,75y,105.51h,87.37t/data=!3m6!1e1!3m4!1sMLZh4r726z6KgjdS4Nc0cg!2e0!7i16384!8i8192

Traffic on Montrose Rd is controlled by the signal at Tower Oaks.  Traffic coming off I-270 off-ramp will continue uninterrupted.  When I drive through here, it is disconcerting if I stop for the red to see other parallel traffic going without stopping, but the traffic from the off-ramp is not controlled by this signal.  This might be a good candidate for a continuous green arrow, to limit confusion, but they seem very rare in MD.

[Revive 755]

Does MUTCD even allow such a thing (where the "same direction" gets different indications)?

The MUTCD seems to contradict itself in this area.  4D.11 Paragraph 02 would allow this:

Option:
Where a movement (or a certain lane or lanes) at the intersection never conflicts with any other signalized vehicular or pedestrian movement, a continuously-displayed single-section GREEN ARROW signal indication may be used to inform road users that the movement is free-flow and does not need to stop.

But this seems to be contradicted by 4D.11 Paragraphs 10 through 12, which prohibits displaying certain signal indications at the same time on the same approach.


Palatine Road in Chicagoland would seem to qualify for this thread with the frontage road signals.

Lake Cook Road at Old Hicks Road in Chicagoland would also qualify with the freeway ramp to westbound getting a perpetual green.

[jeffandnicole]

Also here, near Princeton, NJ.
https://maps.app.goo.gl/oTwQmN4ftn9PqkXv7

[kphoger]

Does MUTCD even allow such a thing (where the "same direction" gets different indications)?

The MUTCD seems to contradict itself in this area.  4D.11 Paragraph 02 would allow this:

Option:
Where a movement (or a certain lane or lanes) at the intersection never conflicts with any other signalized vehicular or pedestrian movement, a continuously-displayed single-section GREEN ARROW signal indication may be used to inform road users that the movement is free-flow and does not need to stop.

But this seems to be contradicted by 4D.11 Paragraphs 10 through 12, which prohibits displaying certain signal indications at the same time on the same approach.

Are we looking at the same edition of the MUTCD?  In the current version, §4D.11 only has 8 paragraphs.

[Ned Weasel]

Here's one example I'm familiar with, where the same signal assembly gives different indicators to two separate roadways serving the same direction of traffic: https://goo.gl/maps/geeGLVEqSdbDPkyR7

[fillup420]

I saw this setup for the first time a while back and thought it was interesting. Although due to the configuration, both sets will never be green at the same time

[johndoe]

Thanks, looks like two more where the parallel approaches are thought of as different legs.  Fillup's is funny to see the marking arrows like that (left turn and right turn pointed at each other).  I hope everyone obeys the "no right on red"!  For Ned's,  I hope that next set of signals don't confuse drivers, or have them see the next green and go

[wanderer2575]

Here's a real winner of a setup on eastbound Main Street (terminus of M-54/M-83) at I-75 in Birch Run:



When the light is green for the traffic turning from the sbd I-75 offramp (on the left), the green right arrow on Main Street lights to allow traffic to continue through the intersection to the sbd I-75 onramp ahead.  There is nothing stopping left-turning traffic from the offramp from pulling into that right lane while it has a green arrow.  I can't believe there hasn't been a major wreck here.

https://goo.gl/maps/N3ZWztMrcBuvLd8q6

[kphoger]

Here's a real winner of a setup on eastbound Main Street (terminus of M-54/M-83) at I-75 in Birch Run:



When the light is green for the traffic turning from the sbd I-75 offramp (on the left), the green right arrow on Main Street lights to allow traffic to continue through the intersection to the sbd I-75 onramp ahead.  There is nothing stopping left-turning traffic from the offramp from pulling into that right lane while it has a green arrow.  I can't believe there hasn't been a major wreck here.

https://goo.gl/maps/N3ZWztMrcBuvLd8q6

Like, just jump into the right lane here, then dart back over into the left lane again–leap-frogging ahead of everyone waiting at the red light?  That loophole could be pretty easily solved by separating the right-turn lane by a double white line instead of a single white line.

[webny99]

Here's a real winner of a setup on eastbound Main Street (terminus of M-54/M-83) at I-75 in Birch Run:
[img]
When the light is green for the traffic turning from the sbd I-75 offramp (on the left), the green right arrow on Main Street lights to allow traffic to continue through the intersection to the sbd I-75 onramp ahead.  There is nothing stopping left-turning traffic from the offramp from pulling into that right lane while it has a green arrow.  I can't believe there hasn't been a major wreck here.

https://goo.gl/maps/N3ZWztMrcBuvLd8q6

Like, just jump into the right lane here, then dart back over into the left lane again–leap-frogging ahead of everyone waiting at the red light?  That loophole could be pretty easily solved by separating the right-turn lane by a double white line instead of a single white line.

I understood the issue to be traffic exiting I-75 turning into the far right lane to re-enter I-75 - which could be a conflict with drivers proceeding through the green arrow.

[roadfro]

Here's a real winner of a setup on eastbound Main Street (terminus of M-54/M-83) at I-75 in Birch Run:
[img]
When the light is green for the traffic turning from the sbd I-75 offramp (on the left), the green right arrow on Main Street lights to allow traffic to continue through the intersection to the sbd I-75 onramp ahead.  There is nothing stopping left-turning traffic from the offramp from pulling into that right lane while it has a green arrow.  I can't believe there hasn't been a major wreck here.

https://goo.gl/maps/N3ZWztMrcBuvLd8q6

Like, just jump into the right lane here, then dart back over into the left lane again–leap-frogging ahead of everyone waiting at the red light?  That loophole could be pretty easily solved by separating the right-turn lane by a double white line instead of a single white line.

I understood the issue to be traffic exiting I-75 turning into the far right lane to re-enter I-75 - which could be a conflict with drivers proceeding through the green arrow.

That was the issue expressed, but it seems like that would be an unlikely maneuver. I would be more concerned with the right turn leap-frogging.

A concrete divider or plastic bollards should really be used in these kinds of situations.