Diverging diamond interchange planned for Wade Green Road
by Geoff Folsom
July 16, 2012 01:11 AM | 5981 views | 17 17 comments | 17 17 recommendations | email to a friend | print

KENNESAW — Cobb’s first diverging diamond interchange is planned for Wade Green Road in Kennesaw and slated to open in late 2014, though county leaders hope to speed that up.

Cobb Commissioners got a preview of the DDI this week from Jeff Lewis, a member of the State Transportation Board. They are expected to give final approval to an agreement with GDOT for the $2.6 million interchange later this summer.

A DDI eliminates a left-turn signal for vehicles accessing freeways, and traffic planners say it is designed to increase capacity and decrease congestion at freeway interchanges. The actual interstate is not altered.

After the technology was introduced in France, Springfield, Mo., was the first city in the United States to get a DDI, in 2009. Last month, the first one in Georgia opened at Ashford-Dunwoody Road over Interstate 285 in DeKalb County. Two others are planned for Gwinnett County.

Dan McDuff, deputy director of Cobb DOT, said the Wade Green project will cost about $2.65 million, with $1 million coming from GDOT for construction and the remaining $1.65 million from the county’s 2011 SPLOST, which will go toward engineering and any additional construction costs. The existing interchange will be retrofitted, and no new lanes will be built.

“This joint venture will ensure timely delivery of the project, cost efficiency and improved mobility for the county, as well as the metro region,” Lewis said.

After allowing traffic to enter the freeway from the right lane, a signaled intersection switches traffic from the right to the left side of the road, where drivers can turn left to enter the freeway without crossing oncoming traffic. Vehicles continuing on the access road then encounter another intersection that switches traffic back to the right side of the road.

Construction of the diverging diamond interchange saved over $100 million over the cost of building a new interchange at Ashford Dunwoody, and is expected to provide congestion relief for at least 10 years, based on traffic growth projections, Lewis said.

At the Wade Green Road interchange, GDOT projects a 60 percent reduction in the amount of time drivers have to wait at traffic lights, along with a 21 percent reduction in overall morning travel times and a 13 percent decrease in evening travel times.

“We know that improved mobility can lead to less commuter frustration, and, something the feds like to hear, can lead to improved air quality,” Lewis said.

An average of 36,000 vehicles per day cross the Wade Green Road bridge, McDuff said. Around 15,000 vehicles will enter Wade Green Road from I-75 northbound, while another 15,000 will enter I-75 southbound. Meanwhile, 5,800 vehicles per day will head north on I-75 from Wade Green Road, while 4,800 driving southbound on I-75 will enter Wade Green Road.

While drivers entering or exiting I-75 can see delays of around a minute in peak times, McDuff said that doesn’t take into account the backups caused by the Wade Green Road interchange. While research hasn’t been done on the entire corridor, McDuff said delays back to Jiles Road can easily reach 10 minutes in the morning.

“When you open this up, it’s going to open things throughout the corridor,” he said.

The Ashford Dunwoody-I-285 interchange, one of 13 diverging diamonds to open in the United States, opened to traffic a month ahead of projected date, Lewis said, and has already resulted in fewer crashes.

The interchanges are considered safer because they eliminate potential crossing conflicts between vehicles turning left onto the freeway while facing opposing traffic, Lewis said. A conventional diamond interchange has four crossing conflicts.

Northeast Cobb Commissioner JoAnn Birrell, whose district includes the area of the proposed interchange, said the project will also benefit the cities of Kennesaw and Acworth. She compares the diverging diamond to roundabouts, another concept that gained popularity in Europe before coming to the United States.

“It’s going to probably be confusing at first, but the drivers will be helped by the islands and the directional signage that make it easier to understand,” Birrell said. “It’s going to be a big benefit down the road.”

GDOT spokesman Mark McKinnon said that at the Ashford Dunwoody interchange, the agency had an extensive public education campaign on the project.

“The signing and the marking makes the expectations pretty intuitive,” he said.

While Cobb DOT has yet to work out the details with GDOT, McDuff said public involvement will be a likely component of developing the interchange.

Commission Chairman Tim Lee also supports the interchange.

“It will be a significant improvement to traffic,” he said. “It will help traffic flow. It will help safety and reduce congestion.”

And more could be coming.

“We’ll evaluate all our interchanges like that to see if that kind of technology will help,” Lee said.

Northwest Cobb Commissioner Helen Goreham said she has yet to see the Ashford Dunwoody-I-285 interchange, but she has heard good things about the diverging diamond interchange.

“Following the news on it, it sounds like it’s fabulous,” she said. “Anything that can help the flow of traffic is wonderful.”

Southeast Cobb Commissioner Bob Ott said the county made sure in the 2011 SPLOST to leave open the possibility of allowing for new technologies to be incorporated. In previous SPLOSTs, rigid language meant the county was locked into a particular type of project, even if the technology changed over the life of the SPLOST.

“What you’re seeing is that they are taking some ideas that worked in other places and bringing them here,” he said.

The development process could delay construction until late 2014, though McDuff said the county is working with GDOT to speed the process up. Once started, construction is expected to take between six and eight months, with the existing interchange remaining open during construction.

McDuff said the Wade Green Road-I-75 interchange, which will also include construction of sidewalks, made sense for the first diverging diamond partly because it won’t require the county to buy new right-of-way.

“The existing bridge will accommodate the proposed interchange, and there will be minimal disruption to businesses in the corridor,” McDuff said. “Also, analysis of the traffic at this location makes it a great candidate with significant reductions in delay after construction.”

Cobb has been discussing the DDI with GDOT for about six months as part of talks to improve congestion at the interchange, McDuff said.

McKinnon said Cobb DOT came to GDOT to propose improvements at Wade Green Road, just as the Perimeter CID initiated discussions on the Ashford Dunwoody Road interchange.

The DDI is the latest road project announced for the area near Kennesaw State University. To the south, the extension of Big Shanty Road will have a ribbon-cutting next week, while the planned bridge connecting Busbee Drive and Frey Road, which is still seeking funding, is expected to provide traffic relief at Chastain Road and I-75.

Comments
(17)
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thePrinter
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July 28, 2012
We live off of Wade Green and can not understand what the fuss is about. Cobb County has not tied the red lites together, and put the sensors in the road to make traffic move using computers to control traffic. At Wade Green the four lanes that feed it as you go north from I-75 really move the traffic in the evening. Yet going south in the morning all traffic goes down a single lane cow pasture to enter I-75. There needs to be the reverse of what is on the other side two turn lanes from each way feeding four lanes funneling traffic on to I-75. A simple fix !!!! Using old and true technology first, before you spend anothe $2.5 Million on this interchange !!!!
Daily Commuter
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July 18, 2012
The above writing is well written to sway our vote to a yes. People should read well and listen to what is being said about untie Atlanta. Funding is the key word that will keep us paying for years. It said nothing about building...and that is where I got a major problem with. Once you vote yes, a lot of people will leave this world without seeing any project for the next 4 to 6 years and I am not sure I will be around. However, voting yes will start that collecting of money until they figure out they have enough and can start whatever project they deemed necessary in all counties involved. I noted that the Untie Atlanta does not have us as part of the people who are deciding on how to use this TSPLOST. It is all of the big guys with their sidekicks making and supporting this TSPLOST thing. My vote is no.......not this time until we see what they actually is going to do and where will that money actually be used for!

Just Saying This
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July 18, 2012
If it were not for greed we could be on the right track of making mass-transportation work! For instant, I-75 should not go into downtown atlanta, rather, an exit off of it if you need to get off, same as all others major interstate highways that running through GA. If those major highways was built for interstate traveling (which means) getting you where you need to go, they should not put you in any situation where you are going to be sitting in traffic because of an accident. Money is the problem. All counties want's its revenue from whatever starts in their counties. Right now, Govenor Deal wants all counties to approve the T-SPLOST, you have to listen to his words. Funding mean for a long period of time, he never said the word building mass transportation; once you vote yes for this upcoming T-SPLOST that means you will be paying for it with your tax dollars for years down the road, 7 to 8, 8 to 9 and 6 to 7 percent sale taxes on everything! Yet, he disapproved the President 50 Billion Transportation bill, he is willing to push your grandmother or seniors out of their homes for you to support the TSPLOST. That is what it mean, paying for it for as long as it is on the planning board and then long after it is completed; "like the GA 400" toll road. That is what this whole thing is about. What you think will end, it will not, and what your state and federal taxes will be, well, you won't like it! What you need to hear should be your concerns rather then hearing what they want you to hear which is good writing to explain why you should vote yes on this TSPLOST. I am voting NO. My sale taxes went from 5 to 6%. I think we are paying equally enough.
Resident of Kennesaw
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July 18, 2012
Major highways such as those we have here in Georgia was not plan well. Even if we have plans for the future; something is done for the mere sake of doing it. As I have seen we like to do things years down the road instead of doing them when we have the funds. Always hitting back at the public for more funds for this and that becomes old news, (because we can) and after it is said and done, we don't have anymore "say so" because...we voted for it. Really, do you all think that you can really solve traffic issues here with "mass transportation, the ARC, trains running here and there; etc. The facts is open and none of are that stupid that any counties traffic woes is going to be solved with this TSPLOST, continuing building roads and changing things around in cities that have already been done over the years. They all find themselves right back into the same of pool. They go nowhere but back into the same of things.
Wasteful Spending
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July 17, 2012
The you for all of the followups, but I don't think the diamond exchange will help until the backlog of rush hour traffic is relieved on I-75.

Surely GDOT could remove the rush hour access delay light, synchronize the traffic lights on the bridge, and take those dollars and apply them to releaving I-75 congestion.

You Legacy Park guys will just get to stop ang go interstate traffic sooner.
anonymous
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July 17, 2012
I have lived on Wade Green Road for almost 30 years. Don't get me wrong, I think it will help, but if the State of Georgia wants to improve traffic problems, then it needs to teach people how to drive.
Bob Bummer
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July 18, 2012
They did it was called driver's ed when I was in school. Apparently it is to expensive for school districts to do this amymore. Although a bit off topic I agree with you.
What Is The Truth?
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July 17, 2012
Continuation of Transportation improvements rings to our pockets and ears each time we pick up a paper or watch the news. Why is it improvements for the future instead of improvements for years gone by with money that is raised from special accessment or whatever that has already been done to get funds be it from us or the government!

Let's face it, we need to live and provide for our families in this economy and would you prefer fixing the roads or taking care of your family because no matter what is said, what has been done, what needs to be done...traffic is still going to be a mess. As always, this also include strip malls, business moving in and creating more traffic on top what we already have so the writing and explaining is good; but that is not the real truth. It's about Atlanta problems and not just Cobb problems, we as citizens can't afford to pay anymore taxes since we have not seen what our other tax dollars have done with the funds we have already given in those previous vote on the 1 percent taxes or whatever you all want to call it. Tim Lee, appear to agree with everything as long as he is in office. We are paying to much to live here on earth. We can't afford anymore. Traffic is what it is...just a complete mess!
anonymous
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July 16, 2012
European in origin, obviously a UN conspiracy to rob us of our individual freedoms.
Bob Bummer
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July 16, 2012
The people that do not travel on Wade Green Road near I-75 between 6 and 9 AM on weekday mornings have no idea how bad the traffic is at the bridge. I suggest getting some first hand knowledge of the situation before claiming this planned construction to be a waste of money. The projected costs to do this are cheap compared to building a mass transit system that will cost us until time ends.
@wasteful spending
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July 16, 2012
Wasteful spending, you obviously do not work, or you do not drive during rush hour across the Wade Green Road bridge. In the peak hours in the morning that interchange will be backed up to Hickory Grove Road on the east side and to Jiles Rd to the west. In peak times it can take between 10 and 15 minutes just to get onto I-75 from the Hickory Gorve intersection. Something needs to be done to increase capacity in that corridor, and this in an excellent low cost solution.

If the TSPLOST was filled with more projects like this oppsosed to silly things like premium bus service and road to nowhere rail lines people might actually support the TSPOLST. 2 million is a cheap construction project for what this will accomplish.
As Expected...
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July 16, 2012
Well that's just perfect: A traffic planning idea that has been in place and used very successfully in Europe for more than 30 years, and "introduced" to the US 9 years ago, is just now finding its way to the vacant halls and heads of Cobb DOT and GDOT.

Right on time, guys. You sure are cutting-edge.

What is it? Too much like work to actually come up with solutions to traffic problems. Oh....I guess it is much easier to just TAX US MORE, and have a few buddy-contractors hang more traffic signals and build more lanes. That'll fix it, right?

What a bunch of hacks.

VOTE NO ON TSPLOST !!! Don't give these buffoons any more money until they show us they know what they are doing.

mk- Cobbs behind
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July 16, 2012
Been through the Ashford D'woody Diamond- very nice, but it's the WHOLE package that's invites big business and quality of life to that area.

Ashford D'woody is 1st class in both directions, south into Chamblee,..lush landscaping, winding sidewalks, stonework walls & seating.

To the north- Perimeter Mall area -feels very cosmopolitan, sophisticated- the walkability/bike lanes/condo highrises/resturants, quality apartments, modern architecture, historic landmarks,..up to Dunwoody & all directions , it's a nice place to live and work & raise a family.

Now look at Cobb Parkway- what an absolute dump!!

And why in the world isn't the Cobb/285 ramp, Spring Road intersection designed correctly and should have been designed and finished 20 years ago.(all that's being done there now is a mess & a waste of time & money!!!)

WHAT is Cobb DOT doing?

All of you need to take a drive through Gwinnett- Back roads , clean, neat,..PIB, landscaped , attractive, check out the Forumn(california look & feel) head through Norcross, Duluth, Suwanee(all 3 are progressive, livable city centers),. then take the ride the 16 mile treck along 85 back to 285. just beautiful!!

Cobb should be ashamed- no excuse to be in the condition we are in! NO EXCUSE!!

Keep ignoring the Windy Hill/75/285 roads, Cobb WILL become 1st official 3rd world metro county!
sircharles
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July 17, 2012
mk, Cobb behind. I was going to mentoned that but I did not want to look down that bad on Cobb County. We do have some good things growing for us and but it appear we don't know how to present it. You mentioned all of those cities and I have been there and you feel wanted, would like to move there. But it will cost you because those are cities broken away from Atlanta or (fulton) county. I do think they were right doing that because they have made much improvements and the cities are very desirable to live, work and place even for families. I do not think a well planned cobb was really consider...I think they were looking for money to quick before they really plan Cobb road ways and landscape and just let things fall where they may. We keep taling about building all of these interchanges, diamonds, cutthroughs, etc., what is really needed for enteire Georgia is to take people where they need to go verse taking them right back into the center of the grady curve, merging on to 75 85 20 etc., those highways should lead you to your appointed destination instead of merging you right back into the Grady curve where tie ups and bang ups often make us sit for hours. Putting all of the major attractions in one place right next to each other create nothing but a complete mess. Finally, this T-SPLOST coming for July 31, 2012, it is not what it is being advertised; from that, strip malls, or new businesses, Art Centers, a new Falcom Stadium and whatever else they want to do with the funding if passed because there is not a set plan as to what they can do with it. Regardless, I am not going to fall for the Yes vote, to much of our money has not been used for what they told us and we voted yes for it! Honesty cost nothing; lies cause you everything and that is why we are in the mess we are in to day because we keep getting told lies about these TSPLOST every time it comes up! The ARC, or the outside highway that takes you around the city which would be called (386) or something; it has been a grave disappointment and the lost of a lot of tax revenues paid in by the Georiga citizens. We can't do it this time!
Diamond21959
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July 16, 2012
So we go from self right people in Dunwoody who run over people, to rednecks who think they deserve to be self right and can't drive.

Guess they realize the traffic lights that stop you to get on a fast moving highway did not work, so someone who has to prove themselves wants to give it a try.
Wasteful Spending
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July 16, 2012
I've lived off of Wade Green Road for the last 14 years. Looks to me that GDOT is just looking for a place to spend tax payers dollars. The money could be better spent elsewhere or return it to the tax payers. What a novel thought.
anonymous
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July 16, 2012
I've lived off Wade Green for last 7 years and i think its a much needed improvement. Traffic is horrible there
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