The multi-faceted improvement project over a 1.43 mile stretch from Cobb Parkway to Powers Ferry Road is expected to be completed by summer 2017.
The estimated $41 million project will be funded by the 2011 Special Purpose Local Option Sales Tax, the Cumberland Community Improvement District, the Georgia Department of Transportation and $1 million coming from grants by the Georgia Transportation Infrastructure Bank, said Jim Wilgus, Cobb Department of Transportation deputy director.
Chairman Tim Lee said the Windy Hill Road improvements will be one of the most important transportation projects undertaken in the next year.
The need for improvements was seen far in advance of the county’s announcement a new Braves stadium would be moving to the Cumberland area, Lee said.
Designs have been underway since 2011, and Lee said the finished product will impact commuters, nearby residents and even freight traffic.
“It starts the ground work for what we need to do in the future,” Lee said.
A 2010 summary of crash and injury data shows the area has a high volume of crashes caused by motorists attempting to cut across middle lanes to get on the I-75 ramp or to make left hand turns into businesses.
A crash history obtained from Cobb DOT said the I-75 intersection with Windy Hill Road ranked as the highest crash location in Cobb.
“Widening the road and adding safety improvements such as medians will create a safer drive for motorists,” Wilgus said.
The Windy Hill Road revamp will be broken down into five areas.
“It was really the funding that separated the project into five different designs,” Wilgus said.
The first three projects will be bid together, Wilgus said, with proposals in July to mid-August
There are two sections on either side of I-75, which Wilgus said will be funded entirely by 2011 SPLOST dollars.
The Windy Hill Road West Project is a 0.74-mile project from Cobb Parkway to the I-75 ramp and the Windy Hill East Project is a 0.37-mile project from Interstate North Parkway West to Powers Ferry Road.
Once completed, both sides will have an additional lane, 20-foot medians and upgraded sidewalks.
On the far-east end of the entire project, a 0.29-mile stretch from Powers Ferry Road to Spectrum Circle will add a westbound lane and replace existing sidewalks.
This section will include GTBI grants, Wilgus said.
This first batch of the three sections should start construction this fall and be completed in two years. Wilgus said it will take a year before work on the roadway begins, because it will take a year to move the large utility poles and lines along Windy Hill Road.
Wilgus said the county has started negotiations for rights of way, which will only involve commercial properties.
The second leg of improvements will be a 0.33-mile project across the I-75 overpass to construct a diverging diamond interchange to decrease traffic congestion and accident rates for motorists using on-off ramps.
Wilgus said bids for the overpass area will go out next July with construction planned to begin in fall 2015.
These upgrades, which will use about 80 percent federal funding, will take about a year to complete, Wilgus said.
The diverging diamond will result in reconstruction of Circle 75, Leland Drive and Interstate North Parkway West. Temporary lane closures will be required for storm drainage and utility construction during the time of construction.
Introducing Cobb residents to the diverging diamond interchange was a bit of a challenge, like other traffic management designs such as roundabouts. But Lee said the region has accepted the new method in traffic engineering.
Confusion over the current traffic patterns leads to tension, Lee said, so the diverging diamond interchange will have a calming effect “with more consistency and safety.”
Although he does not expect the diverging diamond interchange to decrease the time it takes to travel through the area, it will ease the congestion-related issues caused by accidents and fender benders, Lee said.
The final segment at the far east end of the entire plan is a 0.45-mile project on Cobb Parkway and a 0.30-mile portion on Windy Hill Road.
The plans call for adding a median at the intersection of Windy Hill Road and Cobb Parkway, placing turn lanes on the north and south side, lengthening an existing turn lane on the west side and adding five foot sidewalks.