Traffic signal

[SignBridge]

Protected only is very big in some parts of California, notably San Mateo County south of San Francisco. In that county virtually every signalized intersection is protected only whether it seems to need it or not. I was amazed to find this at some relatively low volume traffic intersections where you would not expect to find left-turn arrows at all.

[STLmapboy]

Talk about making use of all the available space on the pole.

[jakeroot]

Likewise, should I counter with there shouldn't be any permissive 2 lane left turns elsewhere because Maine doesn't allow it?

No, because that wouldn't make sense. Maine's policy is being discussed because Maine's new policy would be counter to most other agencies, and thus any data that other said agencies use to support their own policies. The onus is on Maine to prove their more restrictive policy has some basis in reality. Based on the policy of most other places in the US, the answer would appear to be "no".

I would counter: Virtually all other states allow permissive left turns across more than one lane, thus Maine's new policy must be misguided. Unless Maine drivers are just really. that. bad.

Actually,  Maine doesn't have to prove anything to anyone. If Maine wants to mandate a certain traffic control function, its well within their right to do so, regardless what any other state does. If they want federal funding, they would need to make certain they don't run afoul of any federal regulations or guidance, which this does not.

Congrats captain obvious... are you really that dense? I'm not saying Maine has to literally prove that their policy has sound data behind it. They can do whatever the fuck they want.

The general process in most other states is for intersections to gradually progress from fully permissive to fully protected based on individual warrants (such as speeds, number of lanes, turning angles, etc). Maine just threw that entire process out the window. I just want to know why, because even Maine worked that way for decades. Why the change?

[Amtrakprod]

Say there's a two lane approach with #1 lane shared left/through lane and #2 is a through lane, and the left turn is protected only left turns (no permitted movement). If the first car in queue in the #1 shared lane wants to turn left, they are stuck waiting for an arrow–meanwhile, the 10 cars behind that want to go straight are unable to move (or they are darting into the #2 lane when there's a gap). There's your inefficiency.

Atlanta is full of these...and it's very frustrating as someone who grew up in the west where there are very few (if any) of these, and never on major roads.

I would echo your sentiments that these are exceptionally rare (if non-existent) out west, although I have seen them in DC.

Do you have some links to those in Atlanta? I'm curious how they operate. 5-section PPLT signals are not unusual along corridors without turn lanes anywhere in the country, but protected-only left turns along corridors without turn lanes seems really weird to me. Even in DC, where things are already pretty weird as-is, they strike me as a bit odd and perhaps not a good idea.

I guess I didn't read closely enough - these generally aren't protected-only, but they might as well be given the typical very heavy oncoming traffic. Traditionally these used regular doghouse PPLT signals, but most of them now use bimodal FYAs - many in a doghouse configuration (never seen that anywhere else). Here's one example along Piedmont Road, a corridor full of them. Turn around 180 degrees and you'll see how much backup it regularly causes.

I'm not sure I can think of any intersections at all in Utah with a shared left/straight lane that don't use split phasing. Just about every signalized intersection, if there are at least two lanes approaching, has a dedicated left turn lane.

Ah. DC has protected ONLY lefts on split lanes. Really really dumb. If I wasn't on my phone I'd link an example.


iPhone

[jakeroot]

Say there's a two lane approach with #1 lane shared left/through lane and #2 is a through lane, and the left turn is protected only left turns (no permitted movement). If the first car in queue in the #1 shared lane wants to turn left, they are stuck waiting for an arrow–meanwhile, the 10 cars behind that want to go straight are unable to move (or they are darting into the #2 lane when there's a gap). There's your inefficiency.

Atlanta is full of these...and it's very frustrating as someone who grew up in the west where there are very few (if any) of these, and never on major roads.

I would echo your sentiments that these are exceptionally rare (if non-existent) out west, although I have seen them in DC.

Do you have some links to those in Atlanta? I'm curious how they operate. 5-section PPLT signals are not unusual along corridors without turn lanes anywhere in the country, but protected-only left turns along corridors without turn lanes seems really weird to me. Even in DC, where things are already pretty weird as-is, they strike me as a bit odd and perhaps not a good idea.

I guess I didn't read closely enough - these generally aren't protected-only, but they might as well be given the typical very heavy oncoming traffic. Traditionally these used regular doghouse PPLT signals, but most of them now use bimodal FYAs - many in a doghouse configuration (never seen that anywhere else). Here's one example along Piedmont Road, a corridor full of them. Turn around 180 degrees and you'll see how much backup it regularly causes.

I'm not sure I can think of any intersections at all in Utah with a shared left/straight lane that don't use split phasing. Just about every signalized intersection, if there are at least two lanes approaching, has a dedicated left turn lane.

I think it depends on the age of the infrastructure. Most of Utah seems to have pretty new infrastructure. Parts of Washington have older or unwidened infrastructure, thus intersections without direct left turn lanes but with protected/permissive phasing.

Really weird to me that they'd use split phasing when there's no turn lanes. That describes probably 30 to 40% of signalized intersection approaches in Tacoma. Split phasing is normally reserved for intersections with double left turns but where one is an option left/straight lane.

[Revive 755]

Shouldn't you have valid data yourself to support your opinion, rather than "I think there are a lot of counter examples..."

I don't have the time (nor wish to spend the money) filing FOIA's for crash data to research it myself.  If there was always a problem with having permissive lefts across just two opposing through lanes, it's unlikely the Chicago District of IDOT would be allowing new installations of that type.  They seem fairly good at switching over to protected-only lefts if crash problems develop with a left turn movement.

[US 89]

Really weird to me that they'd use split phasing when there's no turn lanes. That describes probably 30 to 40% of signalized intersection approaches in Tacoma. Split phasing is normally reserved for intersections with double left turns but where one is an option left/straight lane.

I don't think I can even think of an intersection in Utah with no turn lanes - almost every traffic light I can think of has at least two approach lanes. But my experience out there is that anything with a shared left/straight lane will be split-phased - even if it's just the one left-turn lane. Here's a prime example of that in Salt Lake.

[mrsman]

Talk about making use of all the available space on the pole.

And the most needed information is actaully left out - the common name of those streets, 9th St and Main St.

The other information, the shields and the guides signs to the next towns usually are placed on ground mounted signs ahead of the intersection.

[mrsman]

Say there's a two lane approach with #1 lane shared left/through lane and #2 is a through lane, and the left turn is protected only left turns (no permitted movement). If the first car in queue in the #1 shared lane wants to turn left, they are stuck waiting for an arrow–meanwhile, the 10 cars behind that want to go straight are unable to move (or they are darting into the #2 lane when there's a gap). There's your inefficiency.

Atlanta is full of these...and it's very frustrating as someone who grew up in the west where there are very few (if any) of these, and never on major roads.

I would echo your sentiments that these are exceptionally rare (if non-existent) out west, although I have seen them in DC.

Do you have some links to those in Atlanta? I'm curious how they operate. 5-section PPLT signals are not unusual along corridors without turn lanes anywhere in the country, but protected-only left turns along corridors without turn lanes seems really weird to me. Even in DC, where things are already pretty weird as-is, they strike me as a bit odd and perhaps not a good idea.

I guess I didn't read closely enough - these generally aren't protected-only, but they might as well be given the typical very heavy oncoming traffic. Traditionally these used regular doghouse PPLT signals, but most of them now use bimodal FYAs - many in a doghouse configuration (never seen that anywhere else). Here's one example along Piedmont Road, a corridor full of them. Turn around 180 degrees and you'll see how much backup it regularly causes.

I'm not sure I can think of any intersections at all in Utah with a shared left/straight lane that don't use split phasing. Just about every signalized intersection, if there are at least two lanes approaching, has a dedicated left turn lane.

Ah. DC has protected ONLY lefts on split lanes. Really really dumb. If I wasn't on my phone I'd link an example.


iPhone

Here's one:

https://www.google.com/maps/@38.9848756,-77.0266865,3a,75y,172.45h,68.76t/data=!3m6!1e1!3m4!1sZ0ND-oNgT3T54lW8P5BNUw!2e0!7i16384!8i8192

IMO, the above signal would be better served with the left lane forcing a left turn.  Especially, since the three lanes merge into two lanes after the next intersection.

I am not happy with ME's one size fits all approach.  turning left across two lanes should generally be OK without protected only signals.

THe option/left seems to make more sense.  A restricted protected only turn will back things up drastically.

[STLmapboy]

Anybody else really like this install? The backplates are a bit wide, but Michigan would do good with more of this.

[JoePCool14]

Anybody else really like this install? The backplates are a bit wide, but Michigan would do good with more of this.

Personally, I'm the exact opposite on this one. I'm really not a fan of those ultra-wide backplates. If you're referring to the fact that the signals are mast-mounted as opposed to span wire-hung... it's okay. Living where I do in Illinois (Wisconsin), I actually like seeing span-wire signals, but that's probably a case of enjoying a change of scenery.

[fwydriver405]

I think are a lot of counter examples across the country with permissive left turns across two through lanes without major crash issues.  Or does Maine have a low bar for what is considered "a high crash location"?

I remember talking about this when I was an intern at my city's DPW back in summer of 2019. Read below:

A High Crash Location (HCL) is a location that has had eight or more traffic crashes and a Critical Rate Factor (CRF) greater than 1.00 in a three-year period. A highway location with a CRF greater than 1.00 has a frequency of crashes that is greater than the statewide average for similar locations. A CRF is a statistical measure to determine the "expected crash rate"  as compared to similar intersections in the State of Maine. In this regard, the analysis considers both the number of crashes and exposure over a three year period.

Sources: MaineDOT, Maine ITE

I'm not sure if this is one of the reasons why they would want to bar permissive left turns across 2+ thru lanes. AFAIK, a majority of our left turn lanes are negative offset and use leading left turns, and until recently, MaineDOT has been reluctant to phase out the 5-section doghouse in favour of the FYA (was told by a MaineDOT offical that they are requiring FYA for all PPLT movements post-2019). As mentioned mutiple times, we still have a high number of PPLT intersections that have yellow trap via phase skip and/or preemption...

----

Semi-related side rant:  Is Maine of those places where left turns are protected only but then are unrestricted left turns to/from other unsignalized side roads and driveways on either side of that intersection?  I am really started to get annoyed with a few locations where I have to wait forever for a green arrow to turn left whereas I could turn right away into a different driveway fifty feet away from the signal.

It sure is. A good example I can think of is at Main St at Alumni/Old Mill Rd in Sanford. The old lights were at the Sanford Plaza (lead) and Integrity Drive (lag), PPLT lead/lag. When our new high school opened on October 10, 2018, the DOT made that intersection all in/right out and moved the lights 100 m (328 ft) to the north. The turn onto Alumni Blvd is now a protected only leading left, the turn onto Old Mill PPLT lagging, and the location of the old intersection is basically a unsignalised left.

Sometimes, especially during light traffic periods, it's actually faster to turn via that unsignalised left then turn right onto Alumni, rather than wait for the green arrow. Red is via the signal, black is the alternative way. (To prevent yellow trap at this intersection, an all red clear is initiated before it can recycle back to that leading left.)

[fwydriver405]

Congrats captain obvious... are you really that dense? I'm not saying Maine has to literally prove that their policy has sound data behind it. They can do whatever the fuck they want.

The general process in most other states is for intersections to gradually progress from fully permissive to fully protected based on individual warrants (such as speeds, number of lanes, turning angles, etc). Maine just threw that entire process out the window. I just want to know why, because even Maine worked that way for decades. Why the change?

You can say the same thing about NHDOT as well. A long time ago, New Hampshire just had the option of just having protected only, or permissive only at many signalised intersections. This resulted in a lot of intersections having protected-only lefts, even on approaches that have excellent sight distance and sufficient gaps to turn into. That was, until 2008-ish when they approved the FYA for use and many intersections are getting an FYA retrofit as a result.

When I went to a job shadow in July 2019 at NHDOT, I asked them about the whole "no permissive lefts across 2+ thru lanes". They said that they have no such policy against that manoeuvre and they rely on other factors, like sight distance, pedestrians, etc. That along with the FYA being mandated in New Hampshire for PPLT is one of the reasons why those turns are very common now.

[fwydriver405]

Not sure if this has been discussed recently, but the 5-section doghouse signal has made it into in Canada for the first time AFAIK, albeit temporarily. This is located in Regina, Saskatchewan at 8th Avenue and Broad St, temporarily replacing a median mounted 4-section bimodal signal for the left turn movement.

Recent sewer work required the median signal pole to be removed, and because the current traffic light pole can't support the weight of all the signals in a row, this style was temporarily installed. These traffic signals will likely be upgraded next year, pending budget approval.

The green advanced left arrow does flash rapidly during the protected phase.

Post from the City of Regina.
Video by CBC about driver reactions.

[STLmapboy]

Not sure if this has been discussed recently, but the 5-section doghouse signal has made it into in Canada for the first time AFAIK, albeit temporarily. This is located in Regina, Saskatchewan at 8th Avenue and Broad St, temporarily replacing a median mounted 4-section bimodal signal for the left turn movement.

Recent sewer work required the median signal pole to be removed, and because the current traffic light pole can't support the weight of all the signals in a row, this style was temporarily installed. These traffic signals will likely be upgraded next year, pending budget approval.

The green advanced left arrow does flash rapidly during the protected phase.

Post from the City of Regina.
Video by CBC about driver reactions.

That CBC video is gold.

[jakeroot]

Yikes!! Their reactions are hilarious.

I actually found a 5-section signal in BC (Production Way @ 200 St, Langley), but it's a tower in keeping with Canadian traditions. Google Earth suggests it was installed around 2002 or 2003.

[STLmapboy]

Yikes!! Their reactions are hilarious.

I actually found a 5-section signal in BC (Production Way @ 200 St, Langley), but it's a tower in keeping with Canadian traditions. Google Earth suggests it was installed around 2002 or 2003.

Per their reactions--I think they're pretty funny, but most American drivers wouldn't instinctively know what to do with a flashing green arrow either. We all have our quirks I guess.

[jakeroot]

Yikes!! Their reactions are hilarious.

I actually found a 5-section signal in BC (Production Way @ 200 St, Langley), but it's a tower in keeping with Canadian traditions. Google Earth suggests it was installed around 2002 or 2003.

Per their reactions--I think they're pretty funny, but most American drivers wouldn't instinctively know what to do with a flashing green arrow either. We all have our quirks I guess.

That's true, although the operation of the signal in the video is identical to what you'd normally see in Canada. It's just the layout.

For once, those in the US are actually the more experienced ones here, since we have all types of 4 and 5 section PPLT signal layouts (with all configurations having heavy use depending on the area), and the new-ish flashing yellow arrow. Canadians are so used to seeing 4-section PPLT signals that literally anything else is just "HUH???". Sure, they have flashing green arrows (and orbs in BC) but the actual layout of the signals is remarkably consistent. I guess, for once, that's not such a good thing.

[STLmapboy]

I found this in Kingdom City MO today (traffic light ground-mount pole sticking right up out of asphalt with very small concrete base). Are there any more examples of traffic lights isolated in pavement?

Opposite direction has a pretty long mast arm devoted to a single left turn signal.

[STLmapboy]

here, FL seems to be replacing a mast arm barely over a decade old with a span wire. At least the poles indicate such.

[jakeroot]

here, FL seems to be replacing a mast arm barely over a decade old with a span wire. At least the poles indicate such.

I'm not sure I've ever seen that kind of pole used to support span-wire signals. Looking at project plans online (check the "project files" section), that pole looks to be placed appropriate for a span wire signal.

If they weren't upgrading the intersection, I think an argument against replacement would be warranted. But two of the signals have to be moved to accommodate widening, so I guess it's just easier to knock everything down and put up a box span or something.

[Amtrakprod]

Not sure if this has been discussed recently, but the 5-section doghouse signal has made it into in Canada for the first time AFAIK, albeit temporarily. This is located in Regina, Saskatchewan at 8th Avenue and Broad St, temporarily replacing a median mounted 4-section bimodal signal for the left turn movement.

Recent sewer work required the median signal pole to be removed, and because the current traffic light pole can't support the weight of all the signals in a row, this style was temporarily installed. These traffic signals will likely be upgraded next year, pending budget approval.

The green advanced left arrow does flash rapidly during the protected phase.

Post from the City of Regina.
Video by CBC about driver reactions.

And I thought Americans were slow lmao. I don't get the big change. Just the orientation?


iPhone

[STLmapboy]

Not sure if this has been discussed recently, but the 5-section doghouse signal has made it into in Canada for the first time AFAIK, albeit temporarily. This is located in Regina, Saskatchewan at 8th Avenue and Broad St, temporarily replacing a median mounted 4-section bimodal signal for the left turn movement.

Recent sewer work required the median signal pole to be removed, and because the current traffic light pole can't support the weight of all the signals in a row, this style was temporarily installed. These traffic signals will likely be upgraded next year, pending budget approval.

The green advanced left arrow does flash rapidly during the protected phase.

Post from the City of Regina.
Video by CBC about driver reactions.

And I thought Americans were slow lmao. I don't get the big change. Just the orientation?


iPhone

Take a listen to the guy's accent at the second link's 1:04 mark.

[Amtrakprod]

Never saw a signal back like these two signal heads in Florence, SC on Cashua Drive at Second Loop Drive.

Who makes these odd looking signal backs?

I was in NY yesterday and saw something similar.


iPhone

[STLmapboy]

Who makes these odd looking signal backs?

I was in NY yesterday and saw something similar.


iPhone

The one on the left is a TCT signal, one on the right is a standard Econolite poly buttonback.