Jake Balentine is a Traffic Designer at Sain. [...]
Sain Associates worked with the Tennessee Department of Transportation (TDOT) to perform the survey and design on a three mile section of Mack Hatcher Parkway (SR-397) from State Route 96 east of Franklin to State Route 6 (US-31) in Williamson County, Tennessee.
This was one of TDOT’s first projects in which the Context Sensitive Design (CSD) process was implemented to formulate a roadway design to complement its surroundings. The CSD process produced a roadway corridor that included a boulevard design with raised grassed median, landscaping, multi-use paths, scenic overlooks, roadway lighting, signalization upgrades, bridges and decorative retaining walls.
One challenge Sain faced was developing a design to stay within the existing 250 to 300-foot right-of-way that was initially purchased with a future widening in mind, but had not envisioned the CSD enhancements that were ultimately added.
Another interesting challenge involved developing an alignment to avoid a battlement of the Roper’s Knob Civil War site while avoiding the reconstruction of an existing bridge over the Harpeth River. Roper’s Knob was the location of a signal station during the Civil War for troops between Nashville and points south and between Franklin and Murfreesboro.
These challenges were overcome by using variations in the roadway typical section, reverse curves in the alignment, and retaining walls.
The contract was let to construction in September 2011 by TDOT for $22,491,186 and is presently under construction with an anticipated completion date of on or before May 15, 2014.