The Florida Department of Transportation (FDOT) District 7 conducted a Project Development and Environment (PD&E) study to evaluate location and design concepts for constructing a southbound C-D road system to carry the southbound on-ramps from SR 56 to I-75 and I-275. The limits of the study are along I-75 from south of the I-75/I-275 Apex to SR 56 in Hillsborough and Pasco Counties. The project improved the southbound operations between the I-75/I-275 and I-75/SR 56 interchanges and eliminated undesirable weaving movements. The design year for the improvements is 2045.
PD&E Study Purpose
The objective of the PD&E study was to assist the FDOT’s Office of Environmental Management (OEM) in reaching a decision on the type, location, and conceptual design of the necessary improvements for the southbound on-ramps from State Road (SR) 56 to Interstate 75 (I-75) and I-275 to safely and efficiently accommodate future travel demand. This study documented the need for the improvements as well as the procedures utilized to develop and evaluate various improvements, including elements such as proposed typical sections, preliminary horizontal alignments, and interchange enhancement alternatives.
The PD&E study satisfied all applicable requirements, including the National Environmental Policy Act (NEPA), to qualify for federal-aid funding of subsequent development phases (design, right-of-way acquisition, and construction). This project was screened through the FDOT’s Efficient Transportation Decision Making (ETDM) process as ETDM Project No. 14330. An ETDM Programming Screen Summary Report was published on February 21, 2018, containing comments from the Environmental Technical Advisory Team (ETAT) on the project’s effects on various natural, physical, and social resources. A Type 2 Categorical Exclusion will be prepared as part of this PD&E study.
Project Purpose and Need
The purpose of the project was to improve operations on southbound I-75 between SR 56 and the southbound off-ramp to I-275 (I-75/I-275 interchange). This project is needed to address the effect on safety and operations by eliminating the need for southbound vehicles to weave in the project area. The proposed improvements are expected to enhance the overall safety and improve the operating conditions within the project limits, as well as improve level of service (LOS) for the southbound I-75 ramp junction with I-275.
Existing Facility and Proposed Improvements
Southbound I-75 north of SR 56 consists of four through lanes. At the connection of the SR 56 southbound ramps to I-75, there are six lanes of traffic. The six lanes of traffic separate to four lanes that continue southbound on I-75 and three lanes that exit to southbound I-275. For vehicles entering I-75 from SR 56 to proceed on southbound I-75, they must weave with southbound I-75 vehicles that are exiting onto southbound I-275. The crash types in this area are indicative of an inadequate weave segment.
The Build Alternative proposed separating vehicles from the SR 56 southbound ramp and I-75 to eliminate the existing weave condition. Traffic from SR 56 would enter a southbound C-D road, separated from I-75 traffic. Lanes on the southbound C-D road would split traffic to I-75 and I-275 and enter the interstates downstream from the existing apex of the I-75/I-275 lane split. Southbound I-75 traffic would exit to southbound I-275 without the influence of southbound traffic from SR 56. A new bridge would be constructed south of County Line Road to carry the I-75 ramp to I-275 over the C-D road ramp to I-75. The proposed improvements would eliminate the traffic weave along I-75 between the entrance ramp to SR 56 and the exit to I-275. Figure 1-2 shows a simplified schematic of the differences between the existing and proposed traffic routes for southbound I-75 and SR 56 ramp to I-275 and I-75 and the elimination of the existing weave zone.
Figure 1-2: Existing and Proposed Traffic Routes for I-75, I-275 & SR 56 Ramp
