TRANSPORTATION

This Interchange Modification Report (IMR) documents the need for improvements at the I-75 and US 301 interchange. The US 301 interchange is located at I-75 Mile Post 10.998 (Mile Marker / Exit Number 224). The study area extends along I-75 from MP 7.816 to MP 11.765. Along US-301, the study area includes I- 75 NB and SB ramps, 51st Avenue signalized intersection to the west, and 60th Avenue signalized intersection to the east (US 301 M.P. 3.855 to M.P. 4.560). The adjacent interchanges are approximately four miles to the noth at I-275 and approximately four miles to the south at SR-64.

The need for interchange improvements at the I-75/US 301 interchange was identified in the Sarasota/Manatee 2035 Long Range Transportation Plan (LRTP). This LRTP stated that increased traffic congestion is anticipated along several major facilities in the area particularly along I-75 and US 301 (Sarasota/Manatee 2035 LRTP, Page 37). Improvements are needed to accommodate future traffic growth due to development in the vicinity of the interchange, and to enhance overall safety, capacity, and emergency evacuation within the County. The existing two loop-ramps located on the NW and NE corners are in conflict with the ultimate I-75 10-lane section approved in the 2009 PD&E study. The 10-lane section consists of 6-lane General Use Lane (GUL) section and 4-lane Special Use Lane (SUL) section.

The purpose of this IMR is to analyze and document the modifications needed to the interchange of I-75 at US 301 in order to accommodate future traffic demand of the year 2038. This IMR reevaluated the preferred interchange concept as developed during the PD&E study that was completed in 2009. Other alternative concepts have also been evaluated based on existing 2012 traffic counts and updated 2038 traffic projections. The currently outdated 2030 FSUTMS SMC (Sarasota-Manatee-Charlotte) regional travel demand model was used in the 2009 PD&E. This IMR used the recently developed 2035 SMCmodel. This model was adjusted to reflect currently planned projects with construction funding through 2014 and those built since 2007. The model used the current projections for the 2035 socioeconomic data and land uses. This IMR will support the on-going design project to reevaluate the configuration of the interchange and the signalized intersections along US 301, within the project limits.

Various interchange concepts were considered during the PD&E study and the early stages of developing this IMR. The interchange concepts evaluation mainly focused on addressing long-term improvements under 2038 Design Year conditions. The following interchange concepts were studied:

Partial Cloverleaf (PARCLO) Interchange with larger NW and NE loop ramps:
This alternative is a modification to the existing partial cloverleaf interchange and incorporates the existing bridge over the Manatee River and US 301 into the design. This concept was discontinued due to the major right of way need associated with the new loop ramps.

Single Point Urban Interchange (SPUI):
A SPUI resembles a slim Diamond Interchange where the ramps are placed close together to make them effectively part of the same intersection. This concept was discontinued as the larger intersection width associated with the SPUI requires greater structure length and depth, which increases the costs for bridge construction, retaining walls, and earthwork.

Diamond Interchange (The 2009 PD&E Preferred Alternative):
This alternative proposes replacing the existing interchange with a diamond configuration and maintaining the existing bridge over the Manatee River and US 301.