If 10th St and the I-75/85 Interchange was designed using Dutch design principles

If 10th St and the I-75/85 Interchange was designed using Dutch design principles, it might be a three-lane turbo roundabout bridge with a bike and pedestrian path bridge parallel but completely separate.

The turbo roundabout was originally conceived to carry several lanes of traffic through a roundabout. Roundabouts are quite complicated to navigate as a driver, so in the Turbo Roundabout, medians and lane markings are designed to guide drivers through to their intended exit without having to do any navigation within the roundabout. Drivers must choose the correct lane before entering the intersection, so lane markings and way finding must be very clear at each entrance. The only other rule is that drivers entering the roundabout should yield to drivers within the roundabout.

The picture below shows a typical turbo roundabout in the Netherlands, this one is located in Pijnacker.

If 10th St and the highway interchange intersection were one big roundabout bridge, it would have to accommodate all movements through 10th St., on and off the highway, and to and from Techwood Dr. and McCamish Pavilion. This is accomplished by giving each entry lane access to only the lane that leads to a certain destination or exit. Since each major approach has three possible movements, each approach would have three lanes. Markings and wayfinding labels painted in the lanes clearly indicate which exit this lane feeds to, and what motion will occur, so that drivers have ample time to decide and maneuver to a lane.

 

Within the roundabout, there are many design elements that guide the vehicle through the crossings to the intended destination. Medians shaped to either deflect or promote movement in certain directions work in conjunction with dashed line striping along the lane to keep the driver in the correct lane. Bumpy and rocky materials on the outside of curves discourage cars from taking a large turn radius but allow trucks to take a larger turn radius with minimal discomfort. Right turns are a bit different than other movements as they can be shaped to feel like a regular right turn instead of a right-left-right swerve (I left the NW right turn as a swerve to compare with the others, especially the SE right turn). To prevent backups, there would be vehicle detection areas far back in each lane (using induction loops or video camera feed) which detect whether a vehicle is waiting, and accordingly changes other approaches’ signals to solid red. This traffic light and yielding access system would provide massive improvements to congestion because it analyzes the set of intersections in real time as a whole system, rather than separate and semi-uncoordinated pre-timed movements.

As for cyclists and pedestrians, there could be no possible way that they could interact with this vehicular traffic; they would require a completely separated underpass. A new separate multi-use path bridge must be built underneath and/or around the roundabout bridge. A multi-use non-vehicular path only requires about 15 feet of clearance.

If 10th St and the I-75/85 Interchange was designed using Dutch design principles, it might look something like this:

 

Go ahead and try to follow each route. Do you go through 10th St for any trips? How would you navigate this roundabout to get home from work, or school, or to Midtown or where ever?

 

(To be truthful, I don’t think this roundabout bridge is at all feasible for this intersection, due to space constraints. It was a nice exercise though, as well as a way to gather ideas to help this intersection, such as the adaptive signals and the separated ped/bike bridge)

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About extremerohit

I'm a Civil Engineering undergrad senior at Georgia Tech. IG: @extremerohit
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