Throughout Gwinnett County, significantly increased traffic volumes combined with limited funding has motivated transportation engineers to develop new options to improve traffic flow. One of these is the "Diverging Diamond" interchange which has been installed at I85 and Jimmy Carter Blvd. and at I85 and Pleasant Hill Road. Another option is the Continuous Flow Intersection, one of which is being scheduled for the intersection of Highways 78 and 124 in Snellville.
At first glance, the operational aspects of these intersections can be confusing, and even after viewing animation videos, it can be difficult to envision how these intersections will improve traffic flow. That's especially true of the Continuous Flow Intersection (CFI) because the name is a bit of a misnomer. "Continuous flow" pertains to straight-through and left turn traffic (traveling in the same direction) flowing at the same time. In a conventional intersection, such as the one at Highway 78 and 124, the light turns green for traffic turning left before it turns green for vehicles traveling straight-through the intersection. This results in extended “red light” times as vehicles traveling through the intersection must wait until traffic turning left clears the intersection before getting a green light.
A CIF addresses this problem by adding left turn lanes on the left side of the roadway which allows left-turning vehicle to cross the highway before they get to the actual intersection. Since they are already on the left side of the roadway, they can pass through the intersection at the same time as vehicles traveling straight through it. That reduces wait time at the intersection. Additional lanes on the right side of the roadway reduce traffic stack-up by enabling vehicles to get out of the main flow of traffic well before they approach the intersection.
The Highway 78/124 intersection modification is primarily a project of the Georgia Department of Transportation (GDOT). The agency's engineers determined that it was the best means of improving traffic flow at the 78/124 intersection, given existing budgetary and geographic constraints. A "flyover" intersection, such as the one at Highway 78 and Park Place in Stone Mountain, would in fact offer continuous flow, however, such an intersection is exponentially more expensive, consumes considerably more land and, for a number of reasons, is inappropriate for the middle of a city like Snellville.
Planning of the CFI which will be built in Snellville may ultimately become a blueprint for other municipalities in dealing with county and state agencies. Snellville's City Council and Downtown Development Authority have been an active participant in the planning process which also includes the Evermore CID and the Gwinnett County and Georgia Departments of Transportation. Although the Snellville city government doesn't have much influence over the actual construction and design of the intersection, by being actively involved in the planning process, it can make sure that execution is as non-invasive as possible. That's especially important because the planned intersection will impact the city's Town Center plan. And the open dialogue between all involved parties amply demonstrates that government agencies at different levels can in fact work with municipal governments to serve the best interests of a local area.