The goal of innovative intersections is to remove left-turn phases from the main intersection. Fewer signal phases can result in reduced delay and increased capacity when compared to a conventional intersection. Below are SYNCHO simulations of a conventional intersection and two innovative intersections. Each simulation has the same traffic volumes, signal cycle lengths, speed limits, and upstream geometry.
The conventional intersection has become the status quo. Multiple-phases reduce the percentage of green time for each phase and increase the loss time each cycle (reducing capacity). While dual left-turns can increase capacity for the left-turn movements, it prevents the left-turns from running permissively (adding delay during off-peak hours). Drivers have become so use to the conventional intersection that they seem not to mind when it takes several cycles to make it through the light.
The median U-turn (also known as the Michigan Left) eliminates left-turns at the main intersection by rerouting left-turn traffic to intersections several hundred feet away. This leads to a simple 2-phase signal at the main intersection which greatly increases capacity. While the median U-turn does increase total capacity, it can be inconvenient for drivers wishing to make a left at the intersection.
A Town Center Intersection (TCI) eliminates left-turn phases while still allowing direct left turns. It does have a big footprint but that can be a selling point since the wide medians (roughly 250-300 feet) provide development opportunities. Gas station or coffee shop owners would love to have their establishments in the median of a major arterial as it provides easy access to their establishment from both directions of travel.
Here's a great link that summarizes a lot of innovative intersections
http://www.compassidaho.org/documents/planning/studies/Vol1_Implementation_Guidelines_Final_May30.pdf (http://www.compassidaho.org/documents/planning/studies/Vol1_Implementation_Guidelines_Final_May30.pdf)
You forgot Jersey Jughandles.
I fancy a good English or diverging intersection, with left turns separated before the junction.
You forgot roundabouts. And Poland.
Here's a list of innovative intersections.
- Continuous Flow Intersection (CFI)
- Parallel Flow Intersection (PFI)
- Town Center Intersections (TCI)
- Quadrant Roadway Intersection (QRI)
- Median U-Turn (Michigan Left Turn)
- Diverging Diamond Interchange (DDI)
- Superstreet
- Jughandles
- Modern Roundabouts
Ban left turns and let god sort traffic out using adjacent streets. Depending on the exact pattern this can be topologically equivalent to a CFI/PFI, QRI, or jughandle, but usually not as efficient geometrically.
PS: a DDI is not like the others. Makes you wonder if there are any no-bridge double DDIs (this would be topologically equivalent to the former I-95/695 interchange with no bridges).
Quote from: NE2 on December 21, 2013, 07:29:44 PM
PS: a DDI is not like the others. Makes you wonder if there are any no-bridge double DDIs (this would be topologically equivalent to the former I-95/695 interchange with no bridges).
Not in this country, at any rate. It's an interesting idea, but you'd either a) still be stuck with 4-phase signal timing, which sucks, or b) have to have the crossovers way back in order to feed traffic through with 2-phase signal timing, which requires a lot of pavement for the left-turn roadways.
Quote from: tradephoric on December 21, 2013, 07:18:21 PM
Here's a list of innovative intersections.
- Continuous Flow Intersection (CFI)
- Parallel Flow Intersection (PFI)
- Town Center Intersections (TCI)
- Quadrant Roadway Intersection (QRI)
- Median U-Turn (Michigan Left Turn)
- Diverging Diamond Interchange (DDI)
- Superstreet
- Jughandles
- Modern Roundabouts
You forgot an Echelon and a Turbine.
Quote from: DaBigE on December 21, 2013, 10:30:15 PM
You forgot an Echelon and a Turbine.
Huh? A turbine is a standard old school freeway-to-freeway design. Might as well list a cloverleaf and a stack.
Why not list the trumpet while your at it. Also there is the windmill interchange that consists of a grade separation and 4 diagonal off ramps leading to the crossing street. (or reverse windmill with 4 onramps)
Quote from: tradephoric on December 21, 2013, 12:48:45 PMA Town Center Intersection (TCI) eliminates left-turn phases while still allowing direct left turns. It does have a big footprint but that can be a selling point since the wide medians (roughly 250-300 feet) provide development opportunities. Gas station or coffee shop owners would love to have their establishments in the median of a major arterial as it provides easy access to their establishment from both directions of travel.
That "TCI" is basically a three-level diamond without the grade-separated through-movements. Can read more about these here http://en.wikipedia.org/wiki/Three-level_diamond_interchange
Have one of those right here in Wisconsin https://goo.gl/maps/9JGrX
However the three level Diamond can be useful for developing over the road or grade separation by decking over the sunken roadway allowing businesses (gas stations, drug stores, grocery, etc) to develop over the two roadways, space permitting of course.
Quote from: hbelkins on December 21, 2013, 12:54:41 PM
You forgot Jersey Jughandles.
I like jughandles but they often don't eliminate all left-turn phases at the main-intersection. Here is a jughandle in Toms River, NJ that does eliminate all left-turn phases juxtaposed with the footprint of a Town Center Intersection (TCI).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FRandom%2FTCIfootprint_zps0a430c20.jpg&hash=4e3d418a79971ef33c4234393c766c106d6e0ae6) (http://s478.photobucket.com/user/tradephoric/media/Transportation%20Pictures/Random/TCIfootprint_zps0a430c20.jpg.html)
All the drawbacks of a cloverleaf, without the benefit of grade separation...
This is a hybrid between a Median U-turn and a Continuous Flow Intersection.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi478.photobucket.com%2Falbums%2Frr144%2Ftradephoric%2FTransportation%2520Pictures%2FRandom%2F1ab308237b311920_landing.jpg&hash=776d7bd6d745a5a55f45621454cc2562fe9aea0a)
The design that tradephoric posted is a proposal. It has not actually begun construction yet.
This intersection is similar to the US 130 and NJ 168 junction near Camden, NJ.
Quote from: roadman65 on December 24, 2013, 10:52:31 PM
This intersection is similar to the US 130 and NJ 168 junction near Camden, NJ.
From all indications, that interchange is a Parallel Flow Interchange. The operational performance of both the CFI and the PFI are similar from what I've read (but the CFI is much more common than the PFI in the US for whatever reason).
Quote from: tradephoric on December 23, 2013, 11:24:52 PM
This is a hybrid between a Median U-turn and a Continuous Flow Intersection.
With this much complexity, at some point, is a grade-separated interchange going to get cheaper?
QuoteWith this much complexity, at some point, is a grade-separated interchange going to get cheaper?
Doubtful. In this case, a grade separation would require some additional right-of-way and would be very complex to build under traffic. Both routes (especially Indian River Rd) are very busy suburban arterials.
Quote from: froggie on December 26, 2013, 07:41:24 AM
QuoteWith this much complexity, at some point, is a grade-separated interchange going to get cheaper?
Doubtful. In this case, a grade separation would require some additional right-of-way and would be very complex to build under traffic.
The added right-of-way could be a problem in terms of cost and other required approvals.
As for building a grade separation with traffic flowing, Maryland SHA has done it quite a few times over the years, and with (relatively) little pain - probably the biggest one I've observed was at U.S. 29 (Columbia Pike) and East Randolph Road in Montgomery County (https://maps.google.com/maps?q=silver+spring+md+20904&hl=en&ll=39.062632,-76.96279&spn=0.004074,0.007929&sll=38.996307,-76.900209&sspn=0.004077,0.007929&t=h&gl=us&hnear=Silver+Spring,+Maryland+20904&z=17). Another big one was at Md. 193 (Greenbelt Road) and Md. 201 (Kenilworth Avenue) (https://maps.google.com/maps?q=greenbelt+md&ll=38.996307,-76.900209&spn=0.004077,0.007929&client=firefox-a&channel=np&hnear=Greenbelt,+Prince+George%27s,+Maryland&gl=us&t=h&z=17) in Greenbelt.
Quote from: froggie on December 26, 2013, 07:41:24 AM
Both routes (especially Indian River Rd) are very busy suburban arterials.
Agreed. Been a long time since I was down that way, but I recall Indian River being pretty busy. In spite of legally being a city, Virginia Beach is in reality one huge and
very suburban place, with a few slices of rural thrown in for good measure near the North Carolina border (outside of the cities around Hampton Roads (Virginia Beach, Chesapeake and Suffolk), I don't think I have seen any other cities in Virginia with as much empty and pretty rural land).