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Author Topic: Single-lane left turns converted from protected-permissive to protected only  (Read 837 times)

SkyPesos

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I found this new 2021 GSV imagery of I-70 in St Charles County (MO) when a construction project was finished. This is at the Route K interchange (exit 217).

2019: During (and before) the interchange redesign project. Protected-permissive left turn with a FYA.

2021: Protected left turn for both onramps. The left turn red light isn't using a red arrow for some reason, something that I haven't seen MoDOT install for at least 8 years. Unrelated, but the left turn arrows on the pavement in the opposite direction is the most misleading thing I've seen so far in traffic signage.

Yes, I know the through movement have an extra lane after construction, but a permissive left turns over 3 lanes of opposing traffic is nothing new.
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Bitmapped

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I don't think this is really all that uncommon. I can think of five intersections within a 15-minute drive of my house that have had one or more movements converted to protected-only. In one case, the opposite movement was converted to a protected-only double left turn and they changed the single-lane side to protected-only to match. The other intersections had sight-distance issues or developed a history of T-bone crashes from people misjudging gaps in traffic.
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jakeroot

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I found this new 2021 GSV imagery of I-70 in St Charles County (MO) when a construction project was finished. This is at the Route K interchange (exit 217).

2019: During (and before) the interchange redesign project. Protected-permissive left turn with a FYA.

2021: Protected left turn for both onramps. The left turn red light isn't using a red arrow for some reason, something that I haven't seen MoDOT install for at least 8 years. Unrelated, but the left turn arrows on the pavement in the opposite direction is the most misleading thing I've seen so far in traffic signage.

Yes, I know the through movement have an extra lane after construction, but a permissive left turns over 3 lanes of opposing traffic is nothing new.

The new design seems like a step backward to me. The red orb is annoying, especially as they have been banned for 10+ years, but the change to protected-only is a little unusual since visibility seems more than adequate. The old design also had better visibility of the signal, at least for southbound traffic, as the overpass limits the visibility of overhead signals.

In one case, the opposite movement was converted to a protected-only double left turn and they changed the single-lane side to protected-only to match.

Could you possibly elaborate as to where this intersection is? I assume in/around the Morgantown, WV area.

jakeroot

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For the most part, the opposite situation is much more common in my area (protected-only to protected-permissive), but switching to protected-only has happened.

One of the most recent examples was Custer Rd @ Bridgeport Way, in Lakewood, WA. The flashing yellow arrow signals were installed around 2014 or 2015, but the westbound approach along Custer Rd was switched to protected-only within the last twelve months. They recently replaced both westbound and eastbound approaches with protected-only three-head left turn signals. I suspect it may have been a time-of-day 'too many cars' issue. Visibility for both approaches seems to have been more than adequate, and the number of lanes doesn't seem like an issue (both northbound and southbound still use FYA signals yet are across three lanes each). Still, wouldn't it have been easier to change to time-of-day phasing? I guess we'll never know.

Another example (also Lakewood, WA) was westbound 84th St at South Tacoma Way (after). Previously, the approach was fully permissive. The left lane was left-only, the middle lane left and straight, and the right lane right-only. When new signals were installed in 2014/2015, the approach was changed to split-phasing. Technically, SkyPesos asked for single-lane examples, but I thought this was interesting enough to include regardless.

fwydriver405

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A lot of existing single lane PPLT's in Maine that cross two or more through lanes will eventually be converted to protected only phasing per new MaineDOT policy (1 (on page 30), 2), as MaineDOT states "this type of movement develops into a high crash location over time". This probably will start becoming more common once the statewide BUILD GRANT commences in end of 2021, and two existing PPLT lefts in my city (Sanford) will be converted to protected only phasing once this project gets to my city (2023). One former PPLT left was converted to a protected only left in 2019 at Main St/Old Mill Rd+Alumni Blvd on the SB Main St approach.

However, there are examples near Bangor that got the reverse treatment (Prot to Perm+Prot, Yield on Green), due to capacity issues. This is an unverified, unofficial policy I was told by some ME engineers, but if PPLT is used across 2+ thru opp lanes, FYA can't be used and are restricted to "Yield on Green" signals. They are:

ME Route 222 at I-95 NB On-ramp (Oct 2016, Sep 2018-present)
Stillwater Ave at Home Depot (Sep 2011, Oct 2016-present)
Main St at Union St (doghouse used for protected only operation) (May 2019, 2020/08/30-present)
Hogan Rd at Longview Dr [initially pm+pt (Sept 2007), then Prot with doghouse (2011-2018), then changed back to pm+pt (Sept 2018-present)]
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Bitmapped

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In one case, the opposite movement was converted to a protected-only double left turn and they changed the single-lane side to protected-only to match.

Could you possibly elaborate as to where this intersection is? I assume in/around the Morgantown, WV area.

Around Morgantown, WV, the intersection of US 19/WV 7 and WV 705 was widened to a double-left turn about 15 years ago for southbound US 19 traffic. Both directions for US 19's left turn lanes now have protected lefts. The single left turn was originally perm/prot after the widening but was eventually changed to protected because of visibility issues with two lanes of opposing traffic.

Northbound on US 19/WV 7 at Boyers Avenue originally was a permitted/protected movement. It was changed to protected-only about 10 years ago. I never heard of a specific reason for the change.

WV 705 at Elmer Prince Drive originally had perm/prot left turns. They were changed to protected-only. The intersection is on a curve and has sight distance limitations.

WV 705 at Stewartstown Road has poor vertical sight lines. WV 705 drops is both directions heading away from the intersection. One side of Stewartstown slopes down into the intersection, and the other side has a downhill heading away from the intersection. The intersection previously was perm/prot for WV 705's left turns, with permitted-only turns on Stewartstown. The intersection has gone through several rounds of widening over the last 15 years. Protected turns were added for both directions of Stewartstown at separate times as each side got a left turn lane. The doghouses on WV 705 were changed to protected-only because of the sight distance limitations.

Monongalia CR 857 at Venture Drive originally had doghouse signals in both directions for CR 857. They were changed to protected-only several years ago after a series of accidents. Traffic normally flows through here around 50mph and there seemed to be problems with people misjudging gaps in oncoming traffic.

In Charleston, WV, US 119 at Oakwood Road previously had a perm/prot turn southbound. It was changed to protected-only several years ago, but the whole intersection was redone this year and converted to an RCUT.
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mrsman

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A lot of existing single lane PPLT's in Maine that cross two or more through lanes will eventually be converted to protected only phasing per new MaineDOT policy (1 (on page 30), 2), as MaineDOT states "this type of movement develops into a high crash location over time". This probably will start becoming more common once the statewide BUILD GRANT commences in end of 2021, and two existing PPLT lefts in my city (Sanford) will be converted to protected only phasing once this project gets to my city (2023). One former PPLT left was converted to a protected only left in 2019 at Main St/Old Mill Rd+Alumni Blvd on the SB Main St approach.

However, there are examples near Bangor that got the reverse treatment (Prot to Perm+Prot, Yield on Green), due to capacity issues. This is an unverified, unofficial policy I was told by some ME engineers, but if PPLT is used across 2+ thru opp lanes, FYA can't be used and are restricted to "Yield on Green" signals. They are:

ME Route 222 at I-95 NB On-ramp (Oct 2016, Sep 2018-present)
Stillwater Ave at Home Depot (Sep 2011, Oct 2016-present)
Main St at Union St (doghouse used for protected only operation) (May 2019, 2020/08/30-present)
Hogan Rd at Longview Dr [initially pm+pt (Sept 2007), then Prot with doghouse (2011-2018), then changed back to pm+pt (Sept 2018-present)]

You said that FYA can't be used.  Is that a Maine policy?  Has the state not adopted FYA signals?

FWIW, in the situations where they are still allowing protective/permissive, FYA would be a far better choice.  For one thing, FYA enables the possibility for time of day left turn restrictions.  You can have protected only during the day (or other busy period) while allowing FYA during off-peak situations.  To the extent that the state is concerned that making a left across more than one lane of traffic as being dangerous, it seems very odd to allow prot/perm doghouse signals in certain towns when a reasonable compromise of TOD signaling is available with FYAs.
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fwydriver405

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You said that FYA can't be used.  Is that a Maine policy?  Has the state not adopted FYA signals?

Correction on that part. MaineDOT has required the FYA for all single lane PPLT left turns crossing 1 thru lane under a new install or retrofit. From what I was told from a few PE's around the Portland area, because of ME's no PPLT across 2+ thru lanes policy, MaineDOT discourages using FYA across two opposing lanes. PPLT can be used across two thru lanes but only if the intersection has demonstrated it operates over-capacity (poor LOS, long queues for example) with protected only left turns.

The Bangor examples I mentioned previously are conversions from Protected only phasing to pm+pt phasing, but this one in Scarborough (before, after) has always been left turn yield on green despite the two opposing thru lanes. Despite new signal heads being installed and a new timing plan, the town elected not to use FYA at this location for some unknown reason.



FWIW, in the situations where they are still allowing protective/permissive, FYA would be a far better choice.  For one thing, FYA enables the possibility for time of day left turn restrictions.  You can have protected only during the day (or other busy period) while allowing FYA during off-peak situations.  To the extent that the state is concerned that making a left across more than one lane of traffic as being dangerous, it seems very odd to allow prot/perm doghouse signals in certain towns when a reasonable compromise of TOD signaling is available with FYAs.

I actually commented about this exact same issue in regards with the Stillwater Ave project in Old Town. Their response:

Quote
My comment: If the two (opposing thru) lanes remain on WB Stillwater Ave, why can’t FYA TOD phasing be used for the WB Stillwater to SB College Ave approach if the “no PPLT against two thru lanes” is an issue? Example: It could be protected only from 6am-7pm everyday, then allow PPLT outside of those hours. It seems very wasteful to have to wait for a green arrow during the “light” traffic periods, especially during the middle of the night.

Response: Presently, FYA to allow for permissive left-turns across 2 on-coming thru lanes are not permitted in Maine. In addition, an engineering study would need to be conducted to justify regulatory signing for time-of-day (TOD) restrictions.

Now I don't know what this regulatory signing is (probably blankout between R10-5 and MA-R10-12a* (LT Yield on FYA)) but MaineDOT is a bit inconsistent about posting LT Yield on FYA signs. They install them at some new or retrofitted intersections, but none of those signs will be posted with the BUILD GRANT construction.

*Sidebar, is there a national standard sign for the "Left Turn Yield on Flashing Yellow Arrow" sign? I've always had to use the MA spec'd sign, MA-R10-12a, since that is the closest thing I can find with official specs. Not sure how other states (including ME) handle this on their sign plans or if they just treat it as a modified R10-12 sign.
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webny99

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Here's an example: Bay Road at NY 104 WB in Webster, NY.

It went from protected/permissive in 2018 to protected-only in 2019. I had no idea why until I looked it up right now, and was surprised to find this news article about the change. It's not a movement I use much, but I can imagine it must be frustrating for those who do. Two lanes is more than adequate for through traffic, allowing considerable space for permissive turns outside of peak hours, so the delays have become significantly longer, even more so than you might expect since the baseline was basically no delay at all. 

I will note this is on a slight curve, and it is the first traffic light on Bay Road southbound (in fact there are very few traffic lights north of NY 104 in this area), so maybe southbound drivers have a tendency to run the light or simply approach faster than expected. Drivers making the left turn might also assume that anyone in the right lane is turning right (where they would have to yield) and be caught off guard by someone going straight.

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US 89

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Here's an example from Utah, on 2600 South (SR 93) at Wildcat Way in Woods Cross, which gets a little more complicated.

pre-2015 (2012): Protected-permissive left turns in both directions from 2600 South, with doghouse signals.

2015: Major reconstruction significantly expands 2600 South, however both left turns from 26th are still single-lane protected-permissive with FYA signals.

2016: Both left turns converted to protected-only.

2021: EB left turn reverted back to protected-permissive with a FYA signal, while WB remains protected-only.

andrepoiy

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There was a few that was solely made during a campaign to "decrease pedestrian fatalities." Includes a conversion to protected left and no-right-on-red.

16th Avenue/Carrville Road at Bathurst Street

Sept 2019:

Sept 2020:

Bayview Avenue at Major Mackenzie Drive

Jul 2019:

Oct 2020:
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fwydriver405

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I almost forgot about a few around the Boston area I always come across.

Kneeland St at the Surface Artery:
pre-2019, "Left Turn Yield on Green"
2019-present, "Left on Green Arrow Only" with 5-section signals

WB Stuart to SB Tremont St. Converted to prot. only phasing due to new bike lanes being installed on both streets:
5-section "Yield on Green", Jun 2018 and before
Conversion to FYA, Aug 2018 - Nov 2020
Permissive phasing removed, Nov 2020-present

Going a bit off tangent here, but there's this one on the O'Brien Highway to Charlestown Ave at where a single lane PPRT was converted to a protected only right turn, again due to bikes. I don't know if the PPRT signal ever operated with concurrent peds:
Oct 2018 and before: PPRT with turns on red permitted
Sept 2019 - present: protected only phasing with turns on red prohibited. Overlap phasing with the compatible perp. left turn

There's probably a few more areas around MA that due to ped/bike protection, pm+pt right turn phasing was converted to prot. only phasing... where those are is the question.
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SkyPesos

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I almost forgot about a few around the Boston area I always come across.

Kneeland St at the Surface Artery:
pre-2019, "Left Turn Yield on Green"
2019-present, "Left on Green Arrow Only" with 5-section signals
This example just seems lazy to me, considering there's already signals to the right for the straight movement. Why not replace the doghouse with a protected only left turn signal here? I think it's better for drivers to see a red left arrow than having to read a sign to understand that left turns are only allowed on a green left arrow.
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roadfro

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I almost forgot about a few around the Boston area I always come across.

Kneeland St at the Surface Artery:
pre-2019, "Left Turn Yield on Green"
2019-present, "Left on Green Arrow Only" with 5-section signals
This example just seems lazy to me, considering there's already signals to the right for the straight movement. Why not replace the doghouse with a protected only left turn signal here? I think it's better for drivers to see a red left arrow than having to read a sign to understand that left turns are only allowed on a green left arrow.

I concur with this. I would never think that a left turn would be protected-only with this type of setup.
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fwydriver405

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I almost forgot about a few around the Boston area I always come across.

Kneeland St at the Surface Artery:
pre-2019, "Left Turn Yield on Green"
2019-present, "Left on Green Arrow Only" with 5-section signals
This example just seems lazy to me, considering there's already signals to the right for the straight movement. Why not replace the doghouse with a protected only left turn signal here? I think it's better for drivers to see a red left arrow than having to read a sign to understand that left turns are only allowed on a green left arrow.

It's funny that 6 blocks to the west of Kneeland / Surface Artery to Stuart at Tremont St, the left turn signal was replaced a total of two times from pm+pt to FYA to prot. only from 2018-2020. Not sure why they replaced the FYA to prot. only in Nov 2020 when they could have just ran the FYA as a prot. only signal full time (don't flash the FYA).

I concur with this. I would never think that a left turn would be protected-only with this type of setup.

My observations going thru that intersection every time I go to Chinatown is most drivers I've seen treat the turn as "Left Turn Yield on Green" despite being signed as "Left on Green Arrow Only".
« Last Edit: October 14, 2021, 11:17:39 AM by fwydriver405 »
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jakeroot

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^^^
The "...on green arrow only" sign appears to be no larger than a postage stamp. I would be surprised if even 10% of drivers notice the sign to begin with.

mrsman

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There was a few that was solely made during a campaign to "decrease pedestrian fatalities." Includes a conversion to protected left and no-right-on-red.


I've seen similar pushes in other areas to move toward protected turns in the name of ped safety as well.  Some times the only discernable change is the change in the left turn signal.  But other times, there are other changes as well to emphasize the safety, such as bike lanes or LPI signals.

Many years ago the intersection of Hilgard/Sunset near UCLA was prot/perm, but it has been proected only for a long time:

https://www.google.com/maps/@34.0782491,-118.4394059,3a,75y,230.16h,74.71t/data=!3m7!1e1!3m5!1s2VWqtMOnWssWa3RqDwIRGA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3D2VWqtMOnWssWa3RqDwIRGA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D78.16926%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

Here is another one.  The road bends here, so visibility is affected.  It is strange that they allowed prot/perm at all for so many years.  Olympic/La Brea.

2007:


https://www.google.com/maps/@34.0573435,-118.3459629,3a,75y,165.31h,71.62t/data=!3m6!1e1!3m4!1sRgk0d4eIU82PWjXJRL8r0A!2e0!7i3328!8i1664

2021:


https://www.google.com/maps/@34.0573274,-118.3458127,3a,75y,167.17h,76.52t/data=!3m7!1e1!3m5!1sCOg0Yr2WH8WqTOn-3epudQ!2e0!5s20210101T000000!7i16384!8i8192



THere are many other corners that went from permitted lefts (no protection at all) to protected only.
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