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U.S. 78 at State Route 124 Improvements

In the end, the process actually justified the alternative

After studying the extreme traffic conditions on U.S. 78 at State Route 124 in Gwinnett County for many years, the Georgia Department of Transportation commissioned GS&P to provide concepts that would finally ease the problems and appease concerned community groups. Local citizens were angered by previous options that would greatly change the landscape of their community and potentially disrupt historic landmarks. Through a series of stakeholder committee workshops, GS&P was able to pinpoint a viable solution that would redirect some traffic onto an underutilized bypass while managing the heavier volumes through an innovative continuous flow intersection (CFI). The solution not only satisfied government and citizen groups alike, but the CFI — the first of its kind in Georgia — will save the state more than $60 million and two to three years of construction time.

Describe the situation that prompted GS&P’s involvement, and the impact the existing environment was having on the community.

Kent Black: The problem involves the intersection of a U.S. route with a state arterial route that provides the gateway to accessing central and east Gwinnett County. This particular intersection has been studied for nearly twenty years. The major traffic delays occurring through this section of the downtown area were impacting economic development. The transportation delays and conflicts on the road system were also a tremendous impact on the pedestrian and bicycle environment. The need was well established, but there had never been a solution that citizens, elected officials, and business owners could rally around.

What is GS&P’s current role in this project?

Jeff Church: Our role is essentially to develop an engineering concept that provides a preferred alternative, and then have an environmental document approved. Once that’s done, then the Department of Transportation will hopefully rehire GS&P under a separate contract to complete the final design services.

Kent: We’re in the environmental phase with GDOT, and, to be honest, the “heavy lifting” on this project is in the concept and environmental process. It becomes a production activity once the concept has been developed and the public involvement, community awareness, and the environmental documents have been signed off on.

What options were first considered as a solution?

Kent: Potential solutions included outer bypasses, local bypasses, and a grade separation at U.S. 78 and SR 124. But all of the previous recommendations were expensive and there was not a consensus, so they never went forward through the county or GDOT work programs. We were challenged with engineering a solution for a problematic intersection location that, unfortunately, is the downtown centerpiece of the city of Snellville. As such, doing grade separation or anything significant would not only be aesthetically displeasing, it would effectively separate the city into two sections, if not three or four, in a fairly pedestrian- and bicycle-unfriendly environment. As we progressed further into the analysis, it became very apparent that grade separation would make it difficult to preserve the environment and historic resources, as well as the interplay between the new city hall area and some of Snellville’s redeveloped areas.

You first had to build some trust with a community that had some significant concerns. Can you explain some of those concerns and what steps you took to alleviate their fears?

Kent: In order to get the community involved in the decision making, we led the Citizens Advisory Committee (CAC). It was a multi tiered strategy, which included a partnering agreement with all CAC members that laid out their roles and responsibilities over this unique year and a half long process.

Scott Shelton: At several CAC meetings, we broke the CAC members up into four or five small work groups with GS&P and GDOT as moderators. This allowed CAC members to ask questions and not feel intimidated, and then the moderator would explain how things work. We also showed animations and aerial displays, which helped build trust with the CAC. The CAC members recognized that they were part of the process of making decisions about the solutions for their city. We developed a robust process that guided them to the best solution while ensuring their support.

As you listened to their concerns, when did you realize that some of the ideas and solutions were actually better than the first suggestions?

Kent: Once the grade-separating solutions were discounted due to extreme impacts, a CFI-type solution became apparent. There are four legs of an intersection in this particular location. The original alternative was a three-legged CFI that would impact three of the four legs. After reviewing the traffic analysis and hearing concerns and input in our CAC workshops about historic resources, we realized the actual preferred alternative was a two-legged CFI. So the process worked to refine the alternative and develop a less impactful solution that still met the objectives of the project.

Scott: At one point, we proposed a bypass we thought might work as a viable solution in the northwest quadrant, but the CAC voiced concerns about that option. After working through it, we conceded that while a three-legged would offer a bit more benefit, it would also create more impact from an engineering and technical standpoint. The single-point urban interchange would provide the most benefit, but also the most impact. So even though we couldn’t give them the Cadillac, we could give them something that would fix the majority of the problem, have less impact, and maintain the core of their city center.

Jeff: It’s also important to realize that as smart as we all think we are, and as much as we thought we had the right idea going into this, none of us had ever been a part of a CFI design before. It was a new concept to us, so we actually went through a learning process as well. We went into the CAC meetings with an open mind as facilitators, which helped us realize the right solution instead of thinking that we were smarter than everybody else. In the end, the process actually justified the alternative.

Elaborate on the tools you used to educate the CAC and how they helped demonstrate your options.

Kent: We did a lot of simulation and animation, which gave them a good forum to understand the alternatives and the constraints and opportunities with each. The detailed traffic analysis that we did of the entire downtown Snellville area was pretty impressive. We not only conducted intersection evaluations but also looked at travel time and delay, origin destination, and pedestrian and bicycle activity in the downtown area. We used VisSim to simulate traffic in the downtown area and develop our recommendations. We also used it as an educational tool to communicate with the CAC and incorporated animation to look at things in three dimensions.

In this complex environment, we needed to be able to show the context of the improvements within the vertical element of the Snellville area, so we used SketchUp and animation to develop a model of what the downtown area looked like. We put our improvements on top of that animation and then placed a simulation of actual cars on top of the roadway network. We built all those layers together to complete our transportation analysis and convince ourselves, from an engineering perspective, that we’d chosen the right solution. The level of traffic simulation and animation was beyond anything we’ve done in the past here in the Atlanta office. It was pretty innovative.

Explain VisSim and what it does.

Kent: VisSim is software that allows you to enter the code for a roadway network and define the attributes of that roadway. You can include the traffic control devices and signals, including the phasing of the signals, so you’re replicating the roadway infrastructure as it currently exists. Then you use actual traffic volume information and future projected volume information, apply it to this network, and calibrate and validate it to existing conditions that we can observe in the field. It provides a reliable framework for us to test various alternatives to the infrastructure, and even design out in the future ten, twenty, or thirty years from now.

Does GS&P have someone who specializes in these types of animated and 3-D displays? Had GDOT ever seen this type of presentation before?

Kent: Jay Bockisch is our project professional for traffic analysis, and the subject matter expert for traffic simulation and modeling for the company. This was all new to GDOT. We took the visuals, animations, traffic analysis, and CAC process a number of steps beyond anything they’d experienced in the past, which will certainly bode well for us in the future when complex projects arise.

Why do you think this project has been so successful to this point?

Scott: A lot of it goes back to the fact that we listened to the CAC and incorporated their feedback. And, what we finally produced with their input wasn’t necessarily what we originally had in mind. The key was listening to them. We even changed the mission statement to include specific wording so that one property owner would agree to it. Their biggest concern was not being heard. Once we met with them, they felt much better.

Jeff: I think it was important that we used a very different approach. Since this was Georgia’s first CFI, getting the Department of Transportation on board was key. Originally, when the grade separation project was conceived, there were several firms around that do that work. As one of many, our odds of winning that project were the same as everyone else. After we determined this was a possible location for a CFI, we set up meetings with GDOT’s traffic and safety personnel, and key decision makers, to educate them on the concept. We didn’t specifically talk about this location, but we educated the department about CFIs, and they were very receptive.

Scott: And it really helped that they understood our commitment. We had previously worked on U.S. 78 to remove the reversal lane system, and a week before that submission was due, GDOT requested some last-minute changes. GDOT was very thankful that we were willing to incorporate updates that late in the process. It really showed them that we were a consultant that cared about the project, valued that intersection and corridor, and would do what was needed to make it a successful solution.


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Project Info

  • Client: Office of Urban Design, Georgia Department of Transportation
  • Location: City of Snellville, Gwinnett County, GA, USA
  • Market: Transportation
  • Services: Engineering
  • Team:
    • Jeffrey B. Church, P.E. Principal-in-Charge
    • Scott Shelton, P.E. Project Manager
    • Kent Black, P.E. Project Professional
    • Jay Bockisch, P.E., PTOE Project Professional
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