TRANSPORTATION

The Florida Department of Transportation, District Three retained Kimley-Horn and Associates, Inc., as part of its Districtwide Safety Studies contract, to perform an Interchange Operational Analysis Report (IOAR) for the interchange of S.R. 8 (I-10) and S.R. 75 (U.S. 231) in Jackson County, Florida. The purpose of this IOAR is to supplement the results of a previously-completed Traffic Signal Warrant Study, which found that existing traffic volumes at the interchange off-ramp terminal intersections and the adjacent intersection of S.R. 75 (U.S. 231) and Dilmore Road warrant the implementation of traffic signal controls at all three intersections.

In accordance with the IOAR Methodology Letter of Understanding, approved in May 2018, this IOAR evaluates the operational efficiency of the three intersections for four analysis periods and three analysis years. Turning movement data collected in July 2017 during the weekday AM, weekend AM, weekday PM, and weekend PM conditions were projected to Opening Year (2021) and Design Year (2031) for evaluation.

The operational analyses, completed using Highway Capacity Software and Synchro, indicate that with the existing stop-controlled conditions, both S.R. 8 (I-10) off-ramp approaches at the ramp terminal intersections on S.R. 75 (U.S. 231) will operate at LOS F during the Design Year (2031) weekend AM conditions and LOS E during the Design Year (2031) weekend PM conditions. With the implementation of traffic signals, all approaches at all three intersections are expected to operate at LOS D or better. A queue analysis found that all existing storage lengths are adequate to accommodate Design Year (2031) conditions for the No Build or the Build scenario.

The safety analysis included an evaluation of the crash history at the S.R. 8 (I-10) interchange and a calculation of the estimated reduction in crashes anticipated with the recommended improvements. Within the area of influence of the subject interchange, 58 crashes were recorded from 2013 to 2017, including two fatal crashes and 20 injury crashes. Based on the recorded crash types and the proposed signalization of the two interchange off-ramp terminal intersections and the adjacent intersection of S.R.75 (U.S. 231) and Dilmore Road, the recommended improvements can be expected to reduce the crash rate by approximately 2.4 crashes per year, yielding an annual safety benefit of approximately $1.1 million.

The two Federal Highway Administration Policy Points for Interchange Access Requests are addressed within this IOAR. Regarding the First Policy Point, the operational and safety analysis included in this IOAR concluded that the proposed traffic signals at the off-ramp terminal intersections do not have significant adverse impact on the safety and operation of S.R. 8 (I-10) or on the local street network based on the future traffic projections. In fact, the proposed traffic signals are anticipated to improve both the safety and the operations of the interchange. A conceptual signing and marking plan for the recommended improvements is included herein. Regarding the Second Policy Point, the recommended improvements in this IOAR apply to the existing S.R. 8 (I-10) and S.R. 75 (U.S. 231) interchange, which provides for all movements to and from the interstate. All movements to and from the interstate will continue to be provided with the implementation of the recommended improvements.