Capitol Square Extension: Innovative Structural Engineering Design Improves Traffic Flow
The Capitol Square Extension involved the construction of a new street connection between Capitol Avenue and Martin Luther King Jr. Drive in the Capitol Hill district of Downtown Atlanta. Creating enhanced mobility, this addition improves the urban landscape in the Capitol Hill area.
As lead designer on the Astra Group, Inc. design-build team, Kimley-Horn provided geometric roadway, structural, and stormwater design, and coordinated the permitting process with the Georgia Department Of Transportation (GDOT) and the City of Atlanta. Our engineers teamed with HGOR for landscape and urban design and R. Powell & Associates for lighting design.
An accelerated one-year timeline was met, and the project was completed within the budget set by Georgia State Financing and Investment Commission (GSFIC) and the Georgia Building Authority. The project finished in time to open the new road for the gubernatorial inauguration and start of the state legislative session.
Innovative Structural Engineering Achieves Client Goals
GSFIC wanted to construct a new street connection in the Capitol Hill district of Downtown Atlanta to help alleviate traffic during events at the Capitol Square plaza and to enhance connectivity downtown. A demolition plan to remove a 1950s-era parking deck and multiple pedestrian bridges was developed to accomplish this. Included in the design were multiple retaining walls to support the new roadway. These innovative structural wall systems were designed to reduce construction costs and avoid significant impacts to the traveling public on I-75/85 and local streets during construction. This design approach also minimized impacts to the capitol plaza and the events that occur there. The retaining wall system used a combination of special design cast-in-place walls and the innovative Gravix precast system to allow for construction of a 40-foot-tall wall in an extremely limited site.
The southbound I-75/85 exit ramp terminal at Martin Luther King, Jr. Drive was also redesigned to improve traffic flow and access from the interstate. The proximity of the intersection to Liberty Plaza and the Capitol Hill district required improved plans for pedestrian crossings and updates for vehicle traffic. Further improvements to the I-75/I-85 southbound exit ramp included a new slip lane that allowed drivers to arrive at state office buildings and parking decks directly, avoiding the one-way pattern that required driving around the Capitol entirely.
Traffic Flow Improvements Enhance Everyday Commutes
The Capitol Square Extension project enhanced connectivity for automobiles and pedestrians in the Capitol Hill area during events and allowed for a more efficient path for commuters and visitors to Georgia’s State Capitol. Easy access to the area was also created for commuters using the I-75/85 and Martin Luther King, Jr. Drive interchange.
Beyond the lasting community impact of the updates to the Capitol Hill district, this project showcases a distinct solution to remove the older infrastructure and construct a new connection that enhances both the mobility and design of the cityscape.
- 2020 Transportation Merit Award Winner; ACEC Georgia Engineering Excellence Awards