Through the project development process, three final build alternatives were selected by the project team for further study. The three alternatives were Alternative 1 (Frontage Road Access Modifications), Alternative 2A (ParClo), and Alternative 2B (DDI). These alternatives included the original preferred alternative for the project and two interchange alternatives. A summary comparison of the three build alternatives is as follows and shown in the Alternatives Comparison Table.
Alternative 1 has the lowest estimated construction cost and is least impactful in terms of anticipated right-of-way, utility, environmental, and structural impacts. However, this alternative was previously dismissed due to not fully and effectively addressing the project purpose and need, as well as public concerns involving increased traffic volumes along the service roads, increased emergency services response times to incidents along mainline SR 0001, and lack of noise mitigation.
When comparing the two interchange alternatives from a traffic operations perspective, both the ParCLO and DDI interchange signalized intersections are expected to operate acceptably in the 2050 design year with all interchange intersections expected to operate at LOS C or better in the ParCLO in both peak hours and LOS B or better in the DDI in both peak hours. The DDI is expected to operate better than the ParCLO at the interchange intersections, which is expected due to the need for only two phases at each of the signalized intersections that is inherent in the DDI design. At other study area intersections adjacent to the interchanges, the ParCLO and DDI alternatives are expected to have similar operations with queues and delay expected to increase at adjacent intersections due to added volume on SR 0413 in both alternatives. However, queues on SR 0413 in the DDI alternative are expected to be longer and potentially impact the SR 0001 southbound off-ramp. In terms of predicted safety performance on the freeway segments, the two alternatives are predicted to be similar. The DDI interchange intersections are predicted to have a slightly lower crash frequency than the other alternatives.
The DDI is expected to be more impactful in terms of right-of-way, structural and access impacts and construction cost. The DDI will impact all four quadrants of the proposed interchange area, requiring more right-of-way, whereas the ParCLO will only have significant impacts to two quadrants. When compared with the ParCLO, the DDI will require either two additional structures or one additional structure and an additional span on the PA 413 (Pine Street) structure over SR 0001 for the proposed SR 0001 Southbound on- and off-ramps to Gillam Avenue. The DDI also removes direct access between PA 413 (Pine Street) and Gillam Avenue and restricts access to Woods Drive to right-in / right-out only on PA 413 (Pine Street). The ParCLO maintains full access between PA 413 (Pine Street) and Gillam Avenue and Woods Drive while also providing a full access interchange between PA 413 (Pine Street) and SR 0001.
Alternative 2A ParCLO was identified as the preferred interchange option for this project area due to addressing the project purpose and need and being less impactful in terms of right-of-way, access, structures and construction cost compared to Alternative 2B DDI.