Diverging Diamond Project at 285/Ashford Dunwoody Starts Next Week
Project will alter highway crossing, bring new design to Georgia
Next week, the Ashford Dunwoody Road Bridge over 285 will begin getting a facelift, bringing a new traffic flow design to the state of Georgia.
Construction crews will start in on the state's first diverging diamond interchange.
When construction is complete, which is expected in September, the new road configuration will have drivers shift to the "wrong side of the road" as they approach either side of the bridge. Drivers heading to I-285 will turn directly onto a ramp without having to cross on-coming traffic. Drivers heading straight through the interchange will return to the "right side of the road" after crossing the bridge.
According to the PCID, the new interchange is expected to reduce traffic delays during evening rush hours up to a projected 15 to 20 percent.
The idea originated in France and will be just the seventh use of the design in the United States since the first was built in Missouri in 2009, according to the Georgia Department of Transportation.
“We think this is going to be something that, once motorists become accustomed to, they will really embrace,” former Georgia DOT Commissioner Vance C. Smith, Jr., said in a press release last fall. “We believe DDIs are going to enable us to make meaningful, relatively inexpensive, improvements at clogged interchanges without having to expend huge amounts of money and time rebuilding the entire structures. We can do DDIs faster and cheaper. And where they have been done, crashes have declined and traffic movement across interchange bridges has improved markedly.”
The design work for the project was paid for by the Perimeter Community Improvement Districts (PCID) and DeKalb County.
In August 2011, GDOT awarded a $4.6 million contract to E.R. Snell Contractors, Inc. of Snellville for the project.
“A number of issues and changes are to be anticipated with a construction project of this type and magnitude,” said Perimeter Community Improvement Districts (PCIDs) Chief Operating Officer David M. Purcell, in a press release.
“While the construction process will not significantly disrupt traffic, a new ramp, sidewalks and pedestrian islands will be built as part of the design,” Purcell said. “As a result, the existing interchange landscape will be replaced with a new stand of trees and landscape plantings to produce a grove-like effect.”
During the last several weeks, the PCIDs have contacted a number of public and non-profit organizations to find possible homes for some of the mature crape myrtles that currently landscape the interchange. These crape myrtles were installed by Perimeter’s business community years ago and their size, along with the large size of other varieties of trees along the interchange, makes any kind of transplantation difficult and expensive.
“Because crapes are hearty, we extended an opportunity for them to be relocated. However, their size, the cost to relocate (around $550 each tree) and no guarantee of survival make it prohibitive for us and most likely for the non-profit organizations we reached out to,” said PCIDs President and CEO Yvonne Williams.
“We do hope to be able to transplant some of the current interchange landscaping, including some of the perennial plantings, in the immediate area. The rest of the shrubs and trees will need to be removed to allow for the construction of the new DDI project, which is critical to maintain the quality of life and grow the economy of the Central Perimeter area,” said Williams.
Mark
6:55 am on Saturday, January 14, 2012
I believe they are also doing this at the Pleasant Hill Road overpass over I-85 in Gwinnett.
Alex H
9:21 am on Monday, January 16, 2012
I recall hearing about that project. I think it is programmed for later this year or next year.
TC
9:46 am on Saturday, January 14, 2012
Another Stupid Idea from Government content on spending money we no longer have!
Jordan Fox
11:26 am on Monday, January 16, 2012
TC, I've heard these sorts of interchanges have worked well in reducing traffic in Europe. I know it's expensive, but what makes you think that it won't work and be well worth the price?
Joni
2:34 pm on Monday, January 16, 2012
I drive the AD Road to 285W to 400N commute and have done this route for 22 years - how in the world is a diverging diamond going to reduce traffic? The same amount of cars will still turn right or left. 285 is not going to magically move faster. I have seen a significant slowdown on my reverse commute since the debacle of the 85 HOT lanes. The only bonus I see is no more sitting at a traffic signal at 5:00AM that is RED with no cars in sight!!
Maybe I am not understanding how the diamond works but from a first glance, it will be one big mess trying to cross back over to the *right* side of the road.
I'm also disappointed to hear the beautiful landscaping will be taken out - why can't the CREPE myrtles be transplanted back to the same spot. They are so very beautiful when they bloom and are such a nice colorful entrance to our neighborhood from the interstate.
Marty
7:07 am on Tuesday, January 17, 2012
It's difficult to see how this is going to resolve the congestion in the area, which comes primarily from the Hammond Dr/Ashford-Dunwoody and the others in front of the mall along Ashford-Dunwoody, and the strange intersection of Ashford-Dunwoody and Johnson Ferry in the other direction.
Joni
7:50 am on Tuesday, January 17, 2012
What is really sickening - yesterday they chopped down most of the trees behind Best Buy!! Why??? Good grief - what do these people have against existing trees. A grove like effect will not make traffic flow smoother and what about the graveyard that is there - how will it be protected? What a waste of our hard earned tax money.
Joni
8:45 am on Tuesday, January 17, 2012
Oops, my bad - the graveyard is behind the the building Best Buy used to be in and is bordered by parking lots
William
2:29 pm on Tuesday, January 17, 2012
Wow...so much anger and not a lot of facts.
1) One of the benefits of the DDI is that is extremely cost effective vs. widening or expanding the bridge over 285. The interchange is going to cost ~$170 Million to reconstruct once the bridge needs replacing, etc. The DDI costs roughly $8M and takes only 9 months or so to complete.
2) Why the DDI is a good stop-gap in this case is probably better left to the engineers...all I know is that it has something to do with the lights and it has worked in other places. Most studies of their use show a 15-20% reduction in congestion and a huge increase in safety through reducing the number of crashes caused by left hand turns. The first in the US was put to use in Missouri in 2009. Here is a write up on the benefits:
http://www.usatoday.com/news/nation/2010-01-27-diverging-diamond-interchange_N.htm
3) As far as landscaping at the Crepe Myrltes, my understanding is the PCID is putting significant resources into lighting, landscaping, and ped improvements to make this intersection an appealing entrance into the area. The existing crepe myrtles are too large to remain during construction but will be replaced by more landscaping....that's my understanding of it.
Joni
2:56 pm on Tuesday, January 17, 2012
@ William - not sure who your *anger* comment is directed to - so I am going to answer - I personally am not angry - just disappointed in the tree loss - there is a BIG difference.
Here ARE some facts...
The left hand turns onto I285 are goverened by turn lights - not yield on green. If there have been crashes, it is because someone ran the light and was hit by a southbound driver. I personally can't remember one recently.
As far as "something to do with the lights" - they are seriously out of sync.
Last week - about 10 of us finally gave up on the turn arrow to get onto 285 so we just ran it after 6 cycles of reds/greens to travel north and south. This happened at 5 am so I really feel sorry for those that hit the major traffic times. The light to get onto AD Rd from I285 was blinking.
Please note - this is a regular occurence - not out of the ordinary.
Again this morning, I sat and sat while waiting for a green arrow to turn left and there were only three cars in sight - all waiting to turn left onto I285
Regardless of how the lanes are reconstructed, I285 is not going to move faster, we'll just get there to sit faster.
Pedestrian crossings do need to be corrected - I'd love to be able to walk to Perimeter Mall because I'm close enough but not brave enough.
Maybe this will work and come fall, I can zip onto I285 and not sit and sit and sit and sit and sit and sit waiting for a left turn arrow.
Danny Marshall
11:23 am on Sunday, January 29, 2012
Disclaimer - I'm not a city planner or civil engineer.
That said, I think a big point that needs to be emphasized is safety. Apparently this creates more "free turns" - which has shown to significantly reduce the number of accidents in studies from diverging diamonds implemented in the Midwest states.
I believe the creation of left turns (think coming down AD from Marist to go west on 285) onto the interstate is supposed to happen with greater flow.
If this can alleviate the congestion on the Best Buy corner, I'm all for it. Cost seems "minimal" compared to reconstructing the bridge.
Naysayers on this project - understand your stance also. If 285 remains congested, it's hard to see how anything done above the highway can really have an impact.