Favorite intersection type?

[tradephoric]

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?

[tradephoric]

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...

[tradephoric]

^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.

[7/8]

Wow, that PFI does look intimidating! 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). It's nice not having to stop when no one's around

[cl94]

Wow, that PFI does look intimidating! 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). 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.

[7/8]

Wow, that PFI does look intimidating! 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). 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.

[johndoe]

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.

[tradephoric]

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

[tradephoric]

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

[tradephoric]

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

[Henry]

Two things come to mind: the NJ jughandle and the MI left.

[tradephoric]

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

[johndoe]

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!

[tradephoric]

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. 

[tradephoric]

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

[Bruce]

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...

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:

[jakeroot]

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.

[jeffandnicole]

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.

[AlexandriaVA]

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.

[tradephoric]

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:

[tradephoric]

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.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

[roadfro]

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.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).

[jakeroot]

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.

[tradephoric]

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

[jakeroot]

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: