As one of the busiest interchanges in the Nashville, Tennessee area, the Interstate 40/ Briley Parkway interchange needed a major design overhaul. But an interchange this busy would have to remain operational during construction, which posed many unique challenges.
The high-volume urban freeway loop corridor connects I-40 to major Nashville destinations such as the Grand Ole Opry, Opryland Hotel, Opry Mills, a major medical center, hotels and other busy commercial complexes. Due to multiple traffic lights the existing interchange was unable to handle the current volumes of traffic. The dangerous weaving patterns required to maneuver on and off the interchange often caused accidents resulting in further delays for commuters and Nashville International Airport traffic.
GS&P's engineers were initially contracted by the Tennessee Department of Transportation (TDOT) in June 1998 to conduct an Interchange Modification Study and recommend lane configurations that would allow the freeway interchange design to operate more efficiently. After TDOT accepted the recommendations, GS&P was directed to proceed with the design phase of the project. Principal-in-charge Michael Flatt, P.E., who led the multidisciplined team throughout the project commented, “This was an extremely challenging project due to the many restrictions surrounding the area.”
The interchange’s close proximity to Nashville International Airport runways and bustling commercial areas posed unique design challenges for the team. The flight path and protected airspace for the airport’s east/west runway crosses directly over this interchange, eliminating the possibility of adding fly-over ramps in certain areas. Nearby hotels, offices and other commercial buildings also severely limited the amount of available right-of-way. Furthermore, another nearby major arterial, Elm Hill Pike, added more traffic feeding the industrial areas that run parallel to I-40.
Several alternatives were explored to minimize the impact on the surrounding stakeholders and for their operational characteristics and costs. The agreed-upon design solution was to vertically stack lanes, remove all signalized ramps, provide direct-connection ramps between I-40 and Briley Parkway and eliminate all dangerous weave areas. Limited right-of-way made horizontal and vertical alignments, as well as clearances and acceptable grade levels, critical throughout the interchange.
To maximize operational efficiency throughout the project, GS&P designed a six-phase traffic control plan that utilized temporary traffic signals and freeway ramps to maintain smooth traffic flow throughout construction. With this design the project was able to reduced vehicle emissions by decreasing traffic idling time, resulting in fuel conservation.
In addition to the miles of new interconnected roads, the work included the construction of 10 bridges, 18 retaining walls and the widening of a 3.15-mile stretch of I-40. GS&P provided construction services for the project which, when it went to contract, was the largest road project ever contracted in Tennessee, costing nearly $66 million. The completed project opened in July 2007.