The folded interchange is an innovative interchange that is similar to a Parclo B4 interchange with diverging diamond characteristics along the arterial. Instead of diverging all traffic along the arterial only left turners who are entering the freeway are diverted and crisscross the opposing left-turners. Below is an existing Parclo B4 interchange at I-526 & Rivers Ave. near Charleston, SC and what a proposed folded interchange would look like:
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That's basically a parclo SPUI. I think I've seen a few that have the ramps meeting under the bridge in a SPUI-like manner, or maybe I'm just recalling Kurumi's spupclo (http://www.kurumi.com/roads/interchanges/oddities.html).
Quote from: NE2 on November 26, 2012, 09:09:36 PM
That's basically a parclo SPUI. I think I've seen a few that have the ramps meeting under the bridge in a SPUI-like manner, or maybe I'm just recalling Kurumi's spupclo (http://www.kurumi.com/roads/interchanges/oddities.html).
Yeah, I'm not sure there are any real-life examples.
I suppose if you have a gigantic median that would work pretty well! :D Unfortunately we don't have many bridges of that length around here. I can't think of any big disadvantages compared to the B4 off the top of my head. Minimal pavement cost increase, and maybe some additional drainage issues.
Here are SimTraffic models of a PARCLO B4 Interchange and a Folded Interchange. Each model is running the same traffic volumes for each turning movement.
The PARCLO B4 is a great interchange design as it improves coordination along the arterial while reducing delays for drivers coming off the freeway (when compared to the PARCLO A4). The Folded Interchange improves on the basic PARCLO B4 design by rerouting left-turners on the arterial. It allows vehicles on the arterial entering onto the freeway to bypass one set of traffic signals improving overall arterial capacity.