Local

I-85/Pleasant Hill Road Converting to Diverging Diamond This Weekend

June 7th, 2013

The Pleasant Hill Road bridge over Interstate-85, in Gwinnett County, is closed this weekend.

Crews are converting the interchange to a diverging diamond format, and if all goes well, the new lanes will be in place by Monday, June 10, at 5 a.m.

A broadcast version of this story

You will not be able to cross the bridge this weekend, but you will be able to get on and off the highway; there will be marked detours set up to get you back on track.

Joe Allen, head of the Gwinnett Place Community Improvement District, says the first time driving through a diverging diamond is a little different. “You will actually shift to the left side, the opposite side of the roadway, as you go across the bridge,” says Allen. “Just basically follow the markings, and you should have no problems making that transition.”

This is the second diverging diamond in the metro area; they are designed to reduce traffic congestion at a much lower price than rebuilding an interchange.

The first one was installed about a year ago at I-285 and Ashford-Dunwoody Road. Analysis of its performance is expected later this year. Officials with the Perimeter Community Improvement Districts, which helped fund that project, say its designers project a reduction in idle time — the amount of time you spend stopped instead of moving – of 20-25 percent.

A third diverging diamond, at I-85 and Jimmy Carter Boulevard, is expected to be up and running next spring.

Here are two videos that may help explain what diverging diamond intersections are and how they work.

First of all, here’s a video that shows the changes that are being made to the Pleasant Hill/I-85 intersection and takes you on a computer-animated drive across the bridge (video created for the Gwinnett Place Community Improvement District).

http://www.youtube.com/watch?v=l7XU-QM4PQI

This video shows a simulation of the diverging diamond intersection at I-285 and Ashford-Dunwoody Road, which was the first such intersection in Atlanta. It’s a time-lapse animation that lets you watch the traffic flows from several angles and get a better feel for how the design works (video created for the Perimeter Community Improvement District).