After reading the favorite interchange thread I thought it would be fun to discuss everyone's favorite intersection type. The focus is on signalized intersections and I think roundabout should be left out of this discussion altogether. There are plenty of standard 4-phase intersections with direct left turns, but more and more innovative intersections are being built as well. So what is everyone's favorite type of intersection out there?
To get things started, a parallel flow intersection is being proposed at the US 41 / SR-54 intersection in Land "˜O Lakes, Florida. I like the fact that it eliminates direct left turns, but OTOH it looks like a total monstrosity! I don't know if I should love it or hate it...
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Few4jVnk.jpg&hash=e803316338a920f2adb6be7470fc9e3201d672de)
^For the amount of space the Parallel Flow Intersection (PFI) would require, it could have been designed as a town center intersection. The ROW is roughly the same for both designs. I like to keep things simple...
https://www.youtube.com/watch?v=eFFw8JDObGA
Some pretty large volumes were plugged into the SYNCHRO model and it didn't seem to trip up the intersection. I don't have actual counts, but it would be interesting to see if a Town Center Intersection (TCI) could have worked at this particular intersection. An advantage of the TCI is that pedestrians would only have to cross 6 lanes of traffic to cross the street as opposed to roughly 18 at the PFI.
Wow, that PFI does look intimidating! :-D Reading up on it, the concept of only needing two signal phases is pretty cool.
I agree that the TCI would be a lot more pedestrian friendly, but is there enough room for it? In your video, you show the TCI overlapping existing buildings and parking lots.
As for the topic question, one intersection type I like is at T-intersections in residential neighbourhoods, sometimes they'll have a yield sign instead of a stop sign on the cross street. I've only seen a couple of these (here's an example in Niagara Falls, ON (https://www.google.com/maps/@43.1131264,-79.1105574,3a,37.5y,186.19h,85.78t/data=!3m6!1e1!3m4!1sL2i6pFw4po6Cd8PU0V21Eg!2e0!7i13312!8i6656)). It's nice not having to stop when no one's around :)
Quote from: 7/8 on August 03, 2016, 06:10:29 PM
Wow, that PFI does look intimidating! :-D Reading up on it, the concept of only needing two signal phases is pretty cool.
I agree that the TCI would be a lot more pedestrian friendly, but is there enough room for it? In your video, you show the TCI overlapping existing buildings and parking lots.
As for the topic question, one intersection type I like is at T-intersections in residential neighbourhoods, sometimes they'll have a yield sign instead of a stop sign on the cross street. I've only seen a couple of these (here's an example in Niagara Falls, ON (https://www.google.com/maps/@43.1131264,-79.1105574,3a,37.5y,186.19h,85.78t/data=!3m6!1e1!3m4!1sL2i6pFw4po6Cd8PU0V21Eg!2e0!7i13312!8i6656)). It's nice not having to stop when no one's around :)
All of those buildings are being taken out anyway. This would probably be a hell of a lot cheaper. Only issue I see is that high left turn volumes could cause gridlock. I don't have SYNCHRO on my personal computer to check it myself, but could you run crazy high opposing left turn volumes in there to see what happens? I'd love to see that.
Quote from: cl94 on August 03, 2016, 06:25:00 PM
Quote from: 7/8 on August 03, 2016, 06:10:29 PM
Wow, that PFI does look intimidating! :-D Reading up on it, the concept of only needing two signal phases is pretty cool.
I agree that the TCI would be a lot more pedestrian friendly, but is there enough room for it? In your video, you show the TCI overlapping existing buildings and parking lots.
As for the topic question, one intersection type I like is at T-intersections in residential neighbourhoods, sometimes they'll have a yield sign instead of a stop sign on the cross street. I've only seen a couple of these (here's an example in Niagara Falls, ON (https://www.google.com/maps/@43.1131264,-79.1105574,3a,37.5y,186.19h,85.78t/data=!3m6!1e1!3m4!1sL2i6pFw4po6Cd8PU0V21Eg!2e0!7i13312!8i6656)). It's nice not having to stop when no one's around :)
All of those buildings are being taken out anyway. This would probably be a hell of a lot cheaper. Only issue I see is that high left turn volumes could cause gridlock. I don't have SYNCHRO on my personal computer to check it myself, but could you run crazy high opposing left turn volumes in there to see what happens? I'd love to see that.
Yeah you're right, thanks for pointing that out. For some reason it looked to me like the TCI took up a lot more room than the PFI, but they're actually about the same size.
I've seen lots of CFI examples, but am unaware of PFI. Any known built examples? I forget the pros and cons of them against one another, but they seem similar in nature. If I remember right the PFI is trademarked, so I assume DOT look to other solutions. I wonder how much it costs to implement the design.
Quote from: johndoe on August 03, 2016, 08:16:35 PM
I've seen lots of CFI examples, but am unaware of PFI. Any known built examples? I forget the pros and cons of them against one another, but they seem similar in nature. If I remember right the PFI is trademarked, so I assume DOT look to other solutions. I wonder how much it costs to implement the design.
Here are the only two PFIs i'm aware of:
US 130 & 168 in Oakley, NJ:
https://www.google.com/maps/@39.9040419,-75.0959415,103m/data=!3m1!1e3
Hard Road & 315 in Columbus, OH: https://www.google.com/maps/@40.1177632,-83.0346222,820m/data=!3m1!1e3
Below is a KMZ file that maps the location of innovative intersections throughout the United States. It's by no means a comprehensive list but some might find it interesting:
https://www.mediafire.com/?z5xac8gntzl50la
Quote from: cl94 on August 03, 2016, 06:25:00 PM
I don't have SYNCHRO on my personal computer to check it myself, but could you run crazy high opposing left turn volumes in there to see what happens? I'd love to see that.
I found 2012 peak hour counts on page 4-15 of the Draft Preliminary Engineering Report for this project:
http://active.fdotd7studies.com/sr54/us41-at-sr54/wp-content/uploads/pdf/Draft_PER_Revised111015withAppendices.pdf
I plugged in these counts into SYNCHRO and recreated the model. It still seems to be holding its own with all approaches clearing in one cycle (but i did have to add dedicated left turn lanes to prevent left-turning traffic from queuing up in the box).
https://www.youtube.com/watch?v=TFQQp1Dy24s
Two things come to mind: the NJ jughandle and the MI left.
I have a soft spot for Michigan Lefts. Detroit corridors are a combination of Michigan Lefts (MUTs) and Restricted Crossing U-Turns (RCUTs). The combination of these innovative intersections allow for some pretty amazing signal progression. Here are some videos the FHWA put together regarding both types of intersections:
https://www.youtube.com/watch?v=fshW_O_XggI
https://www.youtube.com/watch?v=BLwl01NCp9I
Quote from: tradephoric on August 04, 2016, 01:48:47 AM
Below is a KMZ file that maps the location of innovative intersections throughout the United States. It's by no means a comprehensive list but some might find it interesting:
https://www.mediafire.com/?z5xac8gntzl50la
Thanks...is this from alternativeinstersections.org? I can never get that site to work right...the map is always freezing on me!
Yeah, a lot of the locations in that KMZ file were taken from alternativeintersections.org. In addition, i added a lot of jughandle and Michigan left locations than weren't included on that site.
I found this simulation model for the proposed PFI at the intersection of US-41 @ SR-54 in Land 'O Lakes, Florida. It's interesting comparing this simulation model to the Town Center Intersection simulation:
https://www.youtube.com/watch?v=TwE3GzzHIhI
Quote from: tradephoric on August 03, 2016, 03:24:32 PM
To get things started, a parallel flow intersection is being proposed at the US 41 / SR-54 intersection in Land "˜O Lakes, Florida. I like the fact that it eliminates direct left turns, but OTOH it looks like a total monstrosity! I don't know if I should love it or hate it...
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Few4jVnk.jpg&hash=e803316338a920f2adb6be7470fc9e3201d672de)
Jesus christ that looks like a nightmare as someone on foot. 6 crossings to make one simple movement? Across how many lanes? This shouldn't be allowed to exist ever.
My favorite kind of intersection is a one-way couplet with no turns allowed on red. Simple and easy for all parties, no stress involved.
Even more ideally, a raised intersection with speed bumps, bus bulbs, a protected bike lane, and wide sidewalks and a pedestrian scramble.
A dutch junction is also fine if I'm on 2 wheels:
(https://i.ytimg.com/vi/FlApbxLz6pA/maxresdefault.jpg)
Quote from: Bruce on August 08, 2016, 02:13:15 AM
Quote from: tradephoric on August 03, 2016, 03:24:32 PM
To get things started, a parallel flow intersection is being proposed at the US 41 / SR-54 intersection in Land "˜O Lakes, Florida. I like the fact that it eliminates direct left turns, but OTOH it looks like a total monstrosity! I don't know if I should love it or hate it...
http://i.imgur.com/ew4jVnk.jpg
Jesus christ that looks like a nightmare as someone on foot. 6 crossings to make one simple movement? Across how many lanes? This shouldn't be allowed to exist ever.
Totally agree. If the road is that busy, build a god damn overpass or something. This is outrageous.
An overpass would be better for the above intersection...but it appears there's too many nearby businesses to make that feasible. As with most things, how it looks on paper will be a lot different than actually driving it, where signage and lane markings make everything a lot clearer. There are a LOT of lanes though...much more than one normally sees at an intersection.
Bruce's favorite scenario obviously wouldn't work in such a place. I'm sure a lot of people would agree with him, but when you have upwards of 5,000 vehicles or more going thru an intersection per hour, you can't design a single lane intersection for 500 vehicles per hour.
Quote from: jeffandnicole on August 08, 2016, 06:21:05 AM
Bruce's favorite scenario obviously wouldn't work in such a place. I'm sure a lot of people would agree with him, but when you have upwards of 5,000 vehicles or more going thru an intersection per hour, you can't design a single lane intersection for 500 vehicles per hour.
My guess is that the area in question doesn't have a street grid in any sense of the concept, hence the very few nodes that do exist are overloaded, and hence overengineered.
I don't think people realize that you can't have it both ways. If you want your quiet streets with no cut-through traffic, the few intersections of majors roads that do exist are going to be over-burned. It's no different than channeling water around...it eventually has to drain out somewhere.
Looking at the FDOT website for the US41 & SR 54 project I'm not sure if a final alternative has been selected. I found this rendering on the website which shows a grade separated interchange. I personally feel that PFI has no shot at being selected and they will pick something like this instead:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Factive.fdotd7studies.com%2Fsr54%2Fus41-at-sr54%2Fwp-content%2Fuploads%2F2012%2F10%2FSR54_WB_SPUI.jpg&hash=f652475ee106dc20d8b6601b38b26cf64d602aee)
Another Florida intersection worthy of discussion is Bruce B Downs Blvd & Florida 56. The intersection has triple left turns at all approaches and some of the longest continuous crosswalks in all of America (see this thread: https://www.aaroads.com/forum/index.php?topic=5955.msg202152#msg202152).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FCrosswalks%2FFlorida3-lane_zps131a2aca.jpg&hash=b114178c295fd3a5ceaac6d78284b9d992329815)
https://www.google.com/maps/@28.185609,-82.3535353,339m/data=!3m1!1e3
I understand what Florida engineers are thinking. Left turn volumes are high so let's increase the number of left turn lanes. But they are shooting themselves in the foot. By increasing the number of left turn lanes, you are increasing pedestrian crossing distances which in turn increases required cycle lengths in order to fit the pedestrian clearance times. Because the pedestrian crossings are so long, this intersection requires nearly 200 second cycles lengths. Also, with every new MUTCD revision, it seems like the pedestrian design speeds are getting slower and slower (leading to longer required pedestrian clearance time), so the problem is only getting worse as time goes on. Sure, you could have a median to cut down on the total crossing distance but that requires an even wider roadway to fit an adequate median.
The alternative is to eliminate the left turns completely and convert the intersection to a Median U-Turn. Here are SYNCHRO models running as a conventional signal with triple lefts and a Median U-Turn intersection. Each model has the same traffic volumes plugged in but the Median U-Turn can run much shorter cycle lengths (which reduces the amount of queue space). I think Florida needs to get into the innovative intersection game, since the corridors in Florida are often wide enough to fit these innovative intersections into the existing ROW (keeping costs down):
https://youtu.be/8-uaamOekiE
https://youtu.be/BG1-9iF5rtw
Quote from: tradephoric on August 08, 2016, 10:54:06 AM
Another Florida intersection worthy of discussion is Bruce B Downs Blvd & Florida 56. The intersection has triple left turns at all approaches and some of the longest continuous crosswalks in all of America (see this thread: https://www.aaroads.com/forum/index.php?topic=5955.msg202152#msg202152).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FCrosswalks%2FFlorida3-lane_zps131a2aca.jpg&hash=b114178c295fd3a5ceaac6d78284b9d992329815)
https://www.google.com/maps/@28.185609,-82.3535353,339m/data=!3m1!1e3
I understand what Florida engineers are thinking. Left turn volumes are high so let's increase the number of left turn lanes. But they are shooting themselves in the foot. By increasing the number of left turn lanes, you are increasing pedestrian crossing distances which in turn increases required cycle lengths in order to fit the pedestrian clearance times. Because the pedestrian crossings are so long, this intersection requires nearly 200 second cycles lengths. Also, with every new MUTCD revision, it seems like the pedestrian design speeds are getting slower and slower (leading to longer required pedestrian clearance time), so the problem is only getting worse as time goes on. Sure, you could have a median to cut down on the total crossing distance but that requires an even wider roadway to fit an adequate median.
The alternative is to eliminate the left turns completely and convert the intersection to a Median U-Turn. Here are SYNCHRO models running as a conventional signal with triple lefts and a Median U-Turn intersection. Each model has the same traffic volumes plugged in but the Median U-Turn can run much shorter cycle lengths (which reduces the amount of queue space). I think Florida needs to get into the innovative intersection game, since the corridors in Florida are often wide enough to fit these innovative intersections into the existing ROW (keeping costs down):
Hell, they could make this better even without getting into innovative intersection concepts. For the intersection shown, if they had just installed right turn pork chop islands on every approach, they could have cut down the crosswalk length significantly (thus reducing overall required cycle length).
Quote from: roadfro on August 09, 2016, 10:56:01 AM
Hell, they could make this better even without getting into innovative intersection concepts. For the intersection shown, if they had just installed right turn pork chop islands on every approach, they could have cut down the crosswalk length significantly (thus reducing overall required cycle length).
Indeed. Why on earth DOT's have equated fewer crossings with increased safety is beyond me. I've always thought that shorter crossings were safer.
British Columbia uses channelized right turns (right turns with pork chop islands)
a lot along their major arterial roads (chiefly in the suburbs). This particular intersection in
Burnaby Surrey, BC, with its roughly 9-lane crossing (adding together the narrower HOV lanes and the median), is just a hair under 100 feet. But because the right turns are channelized separately from the intersection, minimum green times are much lower than if the right turn lanes were part of the main intersection.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2F6FAmvE9.png&hash=8135a20278ac279938a3fffa0874f7485e271157)
This is one of my favorite intersections from Silver Springs, Maryland. It's a mix between a Median U-turn and a Town Center Intersection:
https://www.google.com/maps/@39.0202079,-77.0126791,321m/data=!3m1!1e3
Quote from: tradephoric on August 12, 2016, 11:38:01 AM
This is one of my favorite intersections from Silver Springs, Maryland. It's a mix between a Median U-turn and a Town Center Intersection:
https://www.google.com/maps/@39.0202079,-77.0126791,321m/data=!3m1!1e3
Functionally, it seems identical to a hamburger roundabout:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwiki.openstreetmap.org%2Fw%2Fimages%2F5%2F58%2FJunction_cut_roundabout_DGT.png&hash=f8150a4a6e28fca2039fcd2905f5c76f2062e965)
Quote from: jakeroot on August 12, 2016, 12:32:43 PM
Functionally, it seems identical to a hamburger roundabout:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwiki.openstreetmap.org%2Fw%2Fimages%2F5%2F58%2FJunction_cut_roundabout_DGT.png&hash=f8150a4a6e28fca2039fcd2905f5c76f2062e965)
Why is movement B allowed? Removing movement B would remove all left turns.
I just read the Utah Department of Transportation is planning to convert Bangerter Highway into a Freeway. This is interesting since 7 CFIs have been built along Bangerter Highway over the past half dozen years. The CFI at Bangerter Hwy and 5400 cost nearly 10 million dollars to build in 2010 and now UDOT is proposing a 60 million grade separated interchange slated for construction in 2017. Only getting 7 years of life out of an innovative intersection that cost nearly 10 million dollars to build doesn't seem like a very wise investment. The concrete alone has 15 years of useful life left in it.
http://www.westjordanjournal.com/2016/04/08/107510/bangerter-highway-to-transform-into-freeway
"Town center intersections", which is just a fancy way of saying one-way pairs.
Quote from: tradephoric on August 03, 2016, 03:24:32 PM
To get things started, a parallel flow intersection is being proposed at the US 41 / SR-54 intersection in Land "˜O Lakes, Florida. I like the fact that it eliminates direct left turns, but OTOH it looks like a total monstrosity! I don't know if I should love it or hate it...
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Few4jVnk.jpg&hash=e803316338a920f2adb6be7470fc9e3201d672de)
That's like a ridiculous souped up (though also different) version of a proposed intersection to be used in a few spots on US-20/26 from Meridian and Boise to Caldwell. (Oh boy does the highway really need widening, most of it is only 2 lanes).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FsSLku7e.png&hash=db5e70677f9c0032383828e94eed5f4c7ffd735a) (http://apps.itd.idaho.gov/apps/us2026CorridorStudy/assets/pdf/2015_PLAN_07-FINAL.pdf)
Quote from: RandomDude172 on August 16, 2016, 10:55:18 AM
I also like this intersection/interchange design (http://www.instructables.com/id/No-Stop-Intersection/), even though I'm not sure it fits the topic, being that it's not signalized. It keeps traffic moving on both streets, and if you want to turn left, you turn around and then turn right, like a Michigan left.
That's just a roundabout under an overpass, grade-separated as an interchange.
Here was the Detroit Rapid Transit Commission's vision of a grade separated intersection in the 1920s. They called them "super-highways" and examples include 8 Mile, Telegraph, Woodward, and Northwestern. These "super-highways" still functioned as surface streets but would be grade separated at major cross-streets.
(https://c1.staticflickr.com/9/8048/8123939316_7bfc84b8ce_o.jpg)
The reality is very few grade separated interchanges were built along these super-highways. Here's a grade-separated interchange that was built at Woodward & 8 Mile in 1956. As you can see they squeezed out the rail lines from the final design. Interestingly, the last streetcar to run down Woodward was on April 8, 1956, the same year this interchange was completed
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FDetroit%2FWoodwardcrossing8mile_zps6d3a2acc.jpg&hash=dbaf70e7ebf45bb17d7f71013e47720211c2bc76)
This picture from 1954 shows the very start of construction at the interchange.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fzm8NXPY.jpg&hash=34a779015e3dea8151e4b15ed0dec77ab018583d)
Quote from: tradephoric on August 04, 2016, 11:28:47 AM
Quote from: cl94 on August 03, 2016, 06:25:00 PM
I don't have SYNCHRO on my personal computer to check it myself, but could you run crazy high opposing left turn volumes in there to see what happens? I'd love to see that.
I found 2012 peak hour counts on page 4-15 of the Draft Preliminary Engineering Report for this project:
http://active.fdotd7studies.com/sr54/us41-at-sr54/wp-content/uploads/pdf/Draft_PER_Revised111015withAppendices.pdf
I plugged in these counts into SYNCHRO and recreated the model. It still seems to be holding its own with all approaches clearing in one cycle (but i did have to add dedicated left turn lanes to prevent left-turning traffic from queuing up in the box).
https://www.youtube.com/watch?v=TFQQp1Dy24s
Just got back to this thread and saw this. Looks like it would work. Wow.
^Another option is a design similar to the Silver Springs, Maryland intersection. Would require less ROW as only one of the roadways would have to widen out.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FMichigan%2520Lefts%2FSSint_zpsui98gksj.png&hash=99fe3f52c378185651b71e76f878a1e409c8cd08)
https://www.google.com/maps/@39.02017,-77.01275,17z/data=!3m1!1e3
Here's a concept for a Michigan Left / roundabout intersection. The problem with this design is people in the E/W direction would also be using the roundabouts to make a U-turn to continue in the N/S directions. Drivers wouldn't have much time to merge into the right most lane to complete their "left turn".
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.alternativeintersections.org%2Fhtml%2Fhome_text%2Fthu%2FThru-Turn-Intersection-Bowtie-with-elipse-1024x355.jpg&hash=2283b34891ae0a0fbc7a814b9b319233725b2235)
Quote from: tradephoric on August 16, 2016, 02:36:21 PM
Here's a concept for a Michigan Left / roundabout intersection. The problem with this design is people in the E/W direction would also be using the roundabouts to make a U-turn to continue in the N/S directions. Drivers wouldn't have much time to merge into the right most lane to complete their "left turn".
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.alternativeintersections.org%2Fhtml%2Fhome_text%2Fthu%2FThru-Turn-Intersection-Bowtie-with-elipse-1024x355.jpg&hash=2283b34891ae0a0fbc7a814b9b319233725b2235)
In most states, it's illegal to turn from the right lane to the left lane. You're supposed to turn from the right-most lane to the right-most lane.
While everyone does such a maneuver above, that's part of the difficulty in designing such concepts. Something that may work in theory isn't always legal.
Quote from: jeffandnicole on August 16, 2016, 03:29:45 PM
In most states, it's illegal to turn from the right lane to the left lane. You're supposed to turn from the right-most lane to the right-most lane.
^I agree. Some states may be hesitant to try certain innovative intersections because of the laws on the books. Of course i think people would adapt. Michigan has the flashing red ball permissive left turn. While technically illegal, it's an unwritten law in Michigan that drivers are allowed to roll through a blinking red at permissive lefts.
A quadrant intersection works pretty well for that Land O'Lakes intersection too. There is a heavy WB left turn movement during peak hour which causes EB through traffic to come to a soft stop, but not horrible. If FDOT was willing to built two quadrants on the SE & NW corner, it would function quite nicely.
https://www.youtube.com/watch?v=uoQP1rcrzbc
The one thing i don't like about FDOT's PFI proposal is that it's just a vast area of asphalt. Sure, it might be extremely effective at moving vehicles through the intersection, but you got to pave an entire city block to accomplish it. A quadrant intersection is essentially a spread out PFI but it allows the opportunity for commercial development in the middle of the intersection. Here's an example of commercial development within the quadrant intersection at Telegraph & Maple in Bloomfield Hills, Michigan:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FMichigan%2520Lefts%2F84_zpshhptonym.jpg&hash=88d6667fadde270fe5ac626d8e33d3b0a81f5539)
Quote from: jeffandnicole on August 16, 2016, 03:29:45 PM
In most states, it's illegal to turn from the right lane to the left lane. You're supposed to turn from the right-most lane to the right-most lane.
You are turning to the nearest lane, but then making two lane changes left :) I've always wondered about that ; is there a rate of legal lane changes ?
The Other way to look at it is that you're supposed to turn into the nearest lane going to your destination...that driver IS turning to the nearest left turn lane.
Quote from: johndoe on August 16, 2016, 08:39:30 PMyou're supposed to turn into the nearest lane going to your destination.
[citation needed]
Quote from: kphoger on August 16, 2016, 09:06:37 PM
Quote from: johndoe on August 16, 2016, 08:39:30 PMyou're supposed to turn into the nearest lane going to your destination.
[citation needed]
Not sure exactly what the law says, but if the law were mine to write, you'd be allowed to turn into the farthest lane IF you are in the center-most turn lane (should that apply), AND your "destination" is within an unreasonably short distance of the intersection.
To be clear, I have no idea what the law is for each state, but at least in my opinion, turning into the farthest lane should be okay if both of the above factors were true.
Quote from: kphoger on August 16, 2016, 09:06:37 PM
[citation needed]
That's fair; quoting what I was told in driver's ed class isn't quite good evidence :) To be honest I don't know the laws, but that's how some roads are designed. Your profile says you're from Kansas, so I picked a random example. Consider the eastbound (EB) approach here: https://goo.gl/maps/pTGo3adkLnA2
For right turns, if you don't want to end up on WB College Blvd you're not going to turn to the immediate lane. For left turns, if you don't want to end up on WB I435 you're not going to turn to the immediate lane. The lefts seem more obvious...it's very common at diamond interchanges. For the rights, as the distance between intersections goes down the odds of people turning to the first lane and weaving goes down. This example is decently long, but I'm sure there are better examples where the auxiliary right turn lane is really short.
Quote from: johndoe on August 16, 2016, 08:39:30 PM
Quote from: jeffandnicole on August 16, 2016, 03:29:45 PM
In most states, it's illegal to turn from the right lane to the left lane. You're supposed to turn from the right-most lane to the right-most lane.
You are turning to the nearest lane, but then making two lane changes left :) I've always wondered about that ; is there a rate of legal lane changes ?
I guess if you want to be completely by the books, you would turn from the right lane to the right lane. Then signal to turn into a lane. In most states, there's a distance required to signal, such as 100 feet. After than 100 feet, then you can merge left. In this case, you would have to merge into the center lane, signal for another 100 feet, then merge into the left lane.
Can you do that in the space provided in the hypothetical example above? Actually, yes...it appears there's time to do that.
Does anyone do that? No. And it would look ridiculous if they did.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.roadsbridges.com%2Fsites%2Frb%2Ffiles%2Fstyles%2Fcontent_image%2Fpublic%2FNo.%252010%2520Road.jpg%3Fitok%3DS7M1Qhm9&hash=f7e601c2a0588271315fc3273831fa0951fa2c91)
https://www.google.com/maps/@39.8678959,-82.9349983,503m/data=!3m1!1e3
This is a RCUT intersection but instead of forcing side-street traffic to make a u-turn, they built a flyover ramp instead (and they threw in a few roundabouts for good measure).
Here's a few examples of offset T-intersections. The are essentially offset RCUT intersections. These intersections allow the main-drag to maintain good signal progression.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FRandom%2Foffsett2_zpsuyjkbxxo.png&hash=9b045147a2f8440f3f1865dfc50ac979681aab03)
https://www.google.com/maps/@42.557264,-83.2857964,703m/data=!3m1!1e3
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FRandom%2Foffset%2520t_zpsucwvos7z.png&hash=d29e8e3112d5a043c14ec6d1bc067c725d47b09b)
https://www.google.com/maps/@42.5280794,-83.356252,349m/data=!3m1!1e3
Quote from: jeffandnicole on August 17, 2016, 08:19:45 AM
Quote from: johndoe on August 16, 2016, 08:39:30 PM
Quote from: jeffandnicole on August 16, 2016, 03:29:45 PM
In most states, it's illegal to turn from the right lane to the left lane. You're supposed to turn from the right-most lane to the right-most lane.
You are turning to the nearest lane, but then making two lane changes left :) I've always wondered about that ; is there a rate of legal lane changes ?
I guess if you want to be completely by the books, you would turn from the right lane to the right lane. Then signal to turn into a lane. In most states, there's a distance required to signal, such as 100 feet. After than 100 feet, then you can merge left. In this case, you would have to merge into the center lane, signal for another 100 feet, then merge into the left lane.
Can you do that in the space provided in the hypothetical example above? Actually, yes...it appears there's time to do that.
Does anyone do that? No. And it would look ridiculous if they did.
I do this whenever possible. For example,
this is a common perspective (https://goo.gl/maps/hkCr78KjMy22) on the way to my house. At the very next side street, I turn right. Do I immediately enter the right lane? No, I enter the left lane, engage my right turn signal, then move right as gradually as possible (which is not very gradual in this instance). Similarly,
at this location nearby (https://goo.gl/maps/jgE14tdLV1R2), most people turning from the right need to move left to get on the main highway. I do not do this: I enter turn into the right lane, then signal my lane changes over into the left lane.
But that's just practice. My point was that the law doesn't say your "supposed to" turn into any lane except the nearest one. Depending on the state, it either says you have to use the nearest one or it doesn't restrict which lane you use at all.
Quote from: tradephoric on August 17, 2016, 10:42:11 AM
...grade separated RCUT ...
Cool, I haven't seen that one before. I've seen it paired with a normal diamond and a SPUI, here's the first time I've seen it with a DDI:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.kansascyclist.com%2Fimg%2Fnews%2F95th%2520DDI.jpg&hash=76670f80a5874f00ab2908620313bb16c272650e)
Time lapse camera: http://www.earthcam.net/projects/kdot/jocogateway/?cam=mpc3
Actually this one just opened today!
Quote from: johndoe on August 17, 2016, 06:10:15 PM
Quote from: tradephoric on August 17, 2016, 10:42:11 AM
...grade separated RCUT ...
Cool, I haven't seen that one before. I've seen it paired with a normal diamond and a SPUI, here's the first time I've seen it with a DDI:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.kansascyclist.com%2Fimg%2Fnews%2F95th%2520DDI.jpg&hash=76670f80a5874f00ab2908620313bb16c272650e)
Time lapse camera: http://www.earthcam.net/projects/kdot/jocogateway/?cam=mpc3
Actually this one just opened today!
Wow! I'm going to have to study this for the next half hour now to figure out how to navigate it. It's probably not that bad driving it but it looks like spaghetti junction from the air!
Quote from: tradephoric on August 18, 2016, 10:13:11 AMWow! I'm going to have to study this for the next half hour now to figure out how to navigate it. It's probably not that bad driving it but it looks like spaghetti junction from the air!
Now this is REALLY cool...drone view!
https://www.youtube.com/embed/EvoLxMTc8Kg
Here's a PFI folded diamond interchange concept. I'm seeing more of these proposed but has one actually been built yet? According to the description in the video ODOT has decided to build a SPUI instead.
https://www.youtube.com/watch?v=7F-RvFyXWlA
Any intersection the good old Kurumi's Me and the Roads wouldn't allow to build :sombrero:.
Quote from: CNGL-Leudimin on August 23, 2016, 06:02:08 PM
Any intersection the good old Kurumi's Me and the Roads wouldn't allow to build :sombrero:.
It was/is pretty restrictive. Code needed to be able to render the intersection and sign assembly.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwisconsindot.gov%2FPublishingImages%2Fsafety%2Fsafety-eng%2Finter-design%2Fechelon800.gif&hash=23d19a59ae73c8620b231b57b4071fd2da46ffcf)
I do like the Echelon Intersection concept. Basically it splits into 2 one way intersections by having one high intersection and one low intersection.
Sorry to grave dig, but here's a cool design I found:
http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/ (http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/)
Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.
What does everyone think?
Quote from: 20160805 on October 06, 2016, 05:48:09 PM
Sorry to grave dig, but here's a cool design I found:
http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/ (http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/)
Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.
What does everyone think?
The concept is interesting, but I don't know that it would work from a practical design standpoint. I don't think the design depicts nearly enough room for the rise/fall of the ramps and doesn't seem like it has appropriate turning radii for larger vehicles.
Quote from: 20160805 on October 06, 2016, 05:48:09 PM
Sorry to grave dig, but here's a cool design I found:
...
What does everyone think?
I'll be even shorter than roadfro: not practical nor realistic. Cartoonish. The design has no basis in reality.
Quote from: 20160805 on October 06, 2016, 05:48:09 PM
Sorry to grave dig, but here's a cool design I found:
http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/ (http://www.efficient-environmental.com/transportation-sustainability-a-free-flow-intersection/)
Advantages are that traffic on both roadways can flow relatively smoothly and you don't need an excessive amount of ROW.
What does everyone think?
My 2 cents: the rendering looks not to scale. Real construction would need a lot more ROW for the 4 interior ramps (spitballing: 5% grade, 20 ft elevation change ==> opposing roadways are 400 feet apart, minimum. A real engineer could provide more accurate numbers.) There are also significant weaving problems at the ramps; this intersection would be free-flowing only in the same way that cloverleaf interchanges are free-flowing: only at low traffic volumes.
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.
Quote from: cl94 on October 16, 2016, 12:45:25 AM
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.
The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).
School buses don't turn on red?
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
The street view even shows independent operation. This is from August (I'm surprised you didn't notice this, trade):
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
It does look like they run independently. The reason why I believed they didn't run independent is because I only saw one signal cabinet on streetview. I'd be curious to see inside that cabinet and I wonder if they have two signal controllers inside that cabinet.
In regards to the FYA, a lot of agencies wouldn't allow permissive lefts when drivers have to cross 3-lane of opposing through traffic (even during off-peak hours). I don't think it's specifically banned in the MUTCD, but that's how a lot of agencies would want to run the show. Similar to how many agencies refuse to allow dual permissive left-turns. I know that example is a sticky one for you, and I didn't mention it to raise your blood pressure, but there are always these agency specific rules that are going to be followed.
Quote from: tradephoric on October 16, 2016, 04:06:15 AM
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
The street view even shows independent operation. This is from August (I'm surprised you didn't notice this, trade):
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
It does look like they run independently. The reason why I believed they didn't run independent is because I only saw one signal cabinet on streetview. I'd be curious to see inside that cabinet and I wonder if they have two signal controllers inside that cabinet.
In regards to the FYA, a lot of agencies wouldn't allow permissive lefts when drivers have to cross 3-lane of opposing through traffic (even during off-peak hours). I don't think it's specifically banned in the MUTCD, but that's how a lot of agencies would want to run the show. Similar to how many agencies refuse to allow dual permissive left-turns. I know that example is a sticky one for you, and I didn't mention it to raise your blood pressure, but there are always these agency specific rules that are going to be followed.
Only raises my blood pressure when people suggest that both (crossing 3+ lanes and dual left yields) are bad ideas because they
think they're bad ideas. The vast majority of studies that I've read consider both to be perfectly acceptable phasing (when constructed properly). Most agencies seem to be afraid of them, hence why so many outright ban both (though I've discovered that here in Washington, where the DOT bans both, individual cities are free to do as they choose; the ones that use permissive across 3+ lanes or dual left yields seem to really like them).
Quote from: jakeroot on October 16, 2016, 02:26:18 AM
Quote from: cl94 on October 16, 2016, 12:45:25 AM
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.
The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).
School buses don't turn on red?
Yeah, thinking about it more, westbound Groveport traffic does back up at times. Plus, Ohio loves its "except curb lane" no turn on red signs.
Quote from: jakeroot on October 16, 2016, 05:24:12 AM
Only raises my blood pressure when people suggest that both (crossing 3+ lanes and dual left yields) are bad ideas because they think they're bad ideas. The vast majority of studies that I've read consider both to be perfectly acceptable phasing (when constructed properly). Most agencies seem to be afraid of them, hence why so many outright ban both (though I've discovered that here in Washington, where the DOT bans both, individual cities are free to do as they choose; the ones that use permissive across 3+ lanes or dual left yields seem to really like them).
I can't fault an agency for wanting to ban permissive left turns in certain scenarios. I've never read a study that concluded permissive left turns are safer than protected left turns. You could argue the agency is being too conservative but they aren't being less safe.
Quote from: jakeroot on October 16, 2016, 02:26:18 AM
Quote from: cl94 on October 16, 2016, 12:45:25 AM
Quote from: jakeroot on October 16, 2016, 12:27:37 AM
Maybe if they swapped the lights to flashing yellow arrows, they wouldn't even need a protected turn phase, outside of rush hour. Lag the flashing yellow arrows with a long phase for Alum Creek, only swap to green arrow if the backup exceeds the storage space.
You'd still need a protected phase for right turns. Imagine getting stuck behind a school bus or another vehicle that doesn't make rights on red.
The right turn lanes could trip the protected turn as well (after a minimum amount of time, of course).
School buses don't turn on red?
School buses and hazmats can't turn on red.
As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.
Quote from: tradephoric on October 16, 2016, 10:31:39 AM
I can't fault an agency for wanting to ban permissive left turns in certain scenarios. I've never read a study that concluded permissive left turns are safer than protected left turns. You could argue the agency is being too conservative but they aren't being less safe.
The studies that I've seen conclude that it isn't any worse with three or more oncoming lanes. Of course, they could eliminate the permissive phase altogether, but if long lines are common at the turn, that can increase driver frustration, particularly when there's no oncoming traffic (and the protected turn was leading, for example).
Quote from: cl94 on October 16, 2016, 02:22:11 PM
School buses and hazmats can't turn on red.
Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).
Quote from: cl94 on October 16, 2016, 02:22:11 PM
As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.
Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.
Quote from: jakeroot on October 16, 2016, 05:07:34 PM
Quote from: cl94 on October 16, 2016, 02:22:11 PM
School buses and hazmats can't turn on red.
Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).
Depends on the state. Many states in the east forbid it and require school buses to have a sticker saying they do not turn on red, New York being one. City buses are often forbidden as well. Can't remember the Ohio law, but I think they're one where you can't turn on red. Don't know about hazmats, but they typically have a sticker saying they won't turn on red as well.
Even if the law allows it, many school bus operators forbid turns on red.
Quote from: jakeroot on October 16, 2016, 05:07:34 PM
Quote from: cl94 on October 16, 2016, 02:22:11 PM
As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.
Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.
Madison has a few for sure (especially along University Ave, west of the UW Campus). Definitely depends on the agency. While WisDOT's signal design manual doesn't explicitly forbid permissive phasing for turns crossing 3+ lanes (it does recommend against it), I can't think of any state installations that employ permissive left turn phasing in that situation.
That was an actual thing. And the light now turns green.
Quote from: jakeroot on October 16, 2016, 05:07:34 PM
Quote from: tradephoric on October 16, 2016, 10:31:39 AM
I can't fault an agency for wanting to ban permissive left turns in certain scenarios. I've never read a study that concluded permissive left turns are safer than protected left turns. You could argue the agency is being too conservative but they aren't being less safe.
The studies that I've seen conclude that it isn't any worse with three or more oncoming lanes. Of course, they could eliminate the permissive phase altogether, but if long lines are common at the turn, that can increase driver frustration, particularly when there's no oncoming traffic (and the protected turn was leading, for example).
Quote from: cl94 on October 16, 2016, 02:22:11 PM
School buses and hazmats can't turn on red.
Is that a federal law? It isn't followed around here. Buses turn on red all the time (no idea about hazmats though).
Quote from: cl94 on October 16, 2016, 02:22:11 PM
As far as permissive turns across 3+ lanes, you generally won't find that in eastern or midwestern states. You just won't. I can only think of a handful of permissives across 3+ lanes.
Very much an agency-by-agency thing. I seem to recall Wisconsin having several, but I could be wrong.
Eau Claire Wisconsin has a dual turn FYA across 2 35mph thru lanes, and now we also have 2 intersections with one approach having dual turn lanes seeing a FYA to cross 3 45mph thru+ a right turn lane. Both of these 45mph intersections operate protected only/protected/permissive during different peak traffic periods.