FDOT District 1, SR 17/Scenic Highway and CR 17B/Hunt Brothers Road Roundabout, Polk County, FL
FDOT District 1|
Protean Design Group removed a two-way flashing beacon and designed a single-lane roundabout at the intersection of SR 17/Scenic Highway and CR 17B/Hunt Brothers Road in Polk County, FL. The design consisted of converting the existing two-lane rural T-intersection with paved shoulders, open drainage, posted speeds of 45 miles per hour (MPH) to 55 MPH, and a flashing signal to a one-lane roundabout with a closed drainage system, Type RA and Type E curb on the inside and Type F curb on the outside lanes, and a landscaped central island with a truck apron. A crash history with several angle and left turn crashes prompted this design. The new roundabout provides the safety benefits of reducing the likelihood for serious injury and fatal crashes due to reduced speeds and removal of impact points. Our design was unique with its ability to accommodate WB 62 semi-trucks, which was required due to the proximity to one of the largest citrus growers and packinghouses in the U.S., while still maintaining a geometry that was safe for standard vehicles.
There were several elements that contributed to the project complexity. The existing right-of-way (ROW) limited the size and layout of the roundabout, but a WB-62FL design vehicle still needed to be accommodated. The approach speed for both roadways was 55 MPH, requiring detailed geometry and signing to safely slow traffic as it enters the roundabout. The location was within a superelevated curve at the bottom of two vertical curves that complicated the approach geometry and required 3D modeling to design the grading of the roundabout. An oval concept was evaluated for consideration but our design was able to accommodate the true roundabout. Gravity wall was utilized at a ditch drop off location to avoid ROW acquisition. Extensive coordination with Florida Department of Transportation (FDOT) and Florida Highway Administration (FHWA) resulted in the development of several alternatives, including non-circular options, to address large truck traffic while still restricting cars to a safe maximum speed.
Numerous innovative concepts were utilized on this unique project. Multiple options were designed including varying radii and non-circular layouts. A “Roundabout Rodeo” was held that utilized a full‐size mockup of the final design to validate the design prior to construction. Milling, resurfacing, and widening were utilized to reuse a majority of the existing pavement. 3D modeling was employed for grading of the roundabout and the superelevated approach. It also enabled accurate overbuild quantities to be calculated. This was a pilot project to employ a new Median-Alert system on the central and splitter islands to increase driver awareness at night. LED lighting was utilized, which requires less maintenance and reduces power consumption.
Sidewalk need and placement was thoroughly evaluated and was not included in the design since there was no pedestrian volume in the corridor. Bicycles are able to utilize the paved outside shoulder facilities and merge with roundabout traffic, as indicated by signage. We added lighting throughout the roundabout.
A Level 2 temporary traffic control plan (TTCP) was utilized and included a detour during the construction of the center island. Traffic was conveyed on existing and temporary pavement.
Protean Design Group supported District 1 with utility coordination by developing the utility conflict matrix and reviewing utility work schedules. One utility agency owner (UAO), Duke Energy, required relocation of their facilities.
A public meeting was held to inform the public of the project and we supported District 1 with coordination with the local citrus grower. FDOT analyzed the environmental impacts since sand skinks were present in the area and concluded there were no significant findings. Landscape architecture was provided by the District’s consultant for the median island and included drought-tolerant plants that required minimal maintenance.
This project received the 2016 FICE/FDOT Outstanding Project Award – Special Project.