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Old 08-16-2014, 12:28 AM
 
394 posts, read 551,920 times
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I saw a story about Jacksonville Florida thinking about implementing a Diverging Diamonds Interchange at of to their I95 exits. This looks like something that may work well at the Wall-Triana/565 exit. Here's a video that explains the concept:

[vimeo]95446053[/vimeo]
Viera Blvd on Vimeo
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Old 08-16-2014, 02:23 AM
 
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It is very useful if there is considerable turning traffic in addition to through traffic. And the intersecting road with the expressway ideally needs to be a divided roadway.

There has been a study going on in Alabama for a couple of years looking at converting the Lakeshore Interchange with I-65 in Shades Valley.

The only one I experience is the I-285 exit at Perimeter Mall in Atlanta. At first it is disconcerting. It does take a couple of trips to become comfortable with what happens. It is really bad for timid drivers or those that are too busy doing other things.

I did come to believe that it is a genius idea. It is much like the Michigan Turns installed on US 280 in Birmingham. It is designed to allow more traffic to keep moving and less traffic having to cross paths.
I am hoping that it is adopted here broadly.

Last edited by raj kapoor; 08-16-2014 at 02:33 AM..
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Old 08-16-2014, 08:46 AM
 
Location: Birmingham
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Pretty neat, never been on one of those. Lakeshore would be a great place for one.
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Old 08-16-2014, 10:01 AM
 
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I see it as an engineer's solution to an interchange with limited space and budget. Ongoing impact is horrible, because it forces two stops of what could be unimpeded traffic during periods of low use on an off ramp time. That means idling vehicles and gas used in accelerating out of stops, along with delays for emergency vehicles.

Clearly, a traditional cloverleaf is smoother in transitioning traffic flows. The space required by the loops can be used in visual parkland. In tight configurations, sometimes flyovers are a better choice.

All in all, I see this as a design with very specific and limited usefulness.
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Old 08-16-2014, 09:34 PM
 
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Quote:
Originally Posted by harry chickpea View Post
I see it as an engineer's solution to an interchange with limited space and budget. Ongoing impact is horrible, because it forces two stops of what could be unimpeded traffic during periods of low use on an off ramp time. That means idling vehicles and gas used in accelerating out of stops, along with delays for emergency vehicles.

Clearly, a traditional cloverleaf is smoother in transitioning traffic flows. The space required by the loops can be used in visual parkland. In tight configurations, sometimes flyovers are a better choice.

All in all, I see this as a design with very specific and limited usefulness.
Yes, you are right, it is definitely meant to be an answer in very urban areas that don't have the land or the money to build an interchange every two miles.

It also will only works efficiently in an area that has the urban traffic load that does not increase the stopping time that you refer to. I suspect that you have not used one or you would realize it is the only road connection other than a multilevel stack that keeps traffic moving in at least two directions at all times.

Actually quite ingenious if you experience it in an area that needs it. Which I don't believe includes this Madison County location.
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Old 08-17-2014, 12:54 PM
 
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Yes, it would be brilliant for Wall Triana x 565.

The problem there is those who want to exit 565 then move over to turn left onto 20. Basically, the current design is a train wreck.

When I was having to do that, I actually exited at the airport, then turned around halfway into the airport. Not ideal, but better than dealing with the Wall Triana x 565/20 garbage.
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Old 08-17-2014, 04:43 PM
 
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Have never seen one of these intersections in person nor had I heard of one prior to this post. Looks like a good solution for very specific intersections with well understood traffic loads and good spacing from other nearby intersections.

I don't see how that design would solve anything at the Wall Triana/I-565 interchange given the nearby proximity of the Wall Triana/Madison Blvd interchange. The biggest issue at that interchange is the closeness of the westbound exit ramp to the Wall Triana/Madison Blvd interchange and the fact that a large percentage of westbound commuters ultimately want to exit the interstate and then cross two lanes and turn left to go westbound on Madison Blvd.
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Old 08-17-2014, 09:24 PM
 
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Once the County Line Interchange is completed, it will alleviate a good amount of congestion. Also, the interchange that will happen just west of Zeirdt will take a lot of the Hughes Rd traffic as well.

What would also be handy is on Intergraph Way, have an entrance to east bound 565.
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Old 08-18-2014, 10:16 AM
 
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I'll need to see which interchanges they are looking at. As a native of Jacksonville, they've had many issues along 95 and 295 with many interchanges. Lots of preserved swamp land prevents building large clover interchanges. Large flyovers take forever to build because the sandy soil doesn't provide adequate support unless structurally designed properly. There is a flyover interchange at I-95 and 295 on the south end of town that took 6 years to complete because of support issues.
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Old 08-19-2014, 09:32 AM
 
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Why not just make one of those crossovers crossover and not have any traffic stop.
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