Alternative 4c is an option of Alternative 4. What is Alternative 4?
Alternative 4 – Efficient Interchange Reconstruction – is one of five evaluated in the Alternatives Screening Report for the North Split. Alternatives 1, 2 and 3 were eliminated because they would not meet the project purpose and need. Alternative 4 would meet the project purpose and need without providing added through lanes. Alternative 5 – Full Interchange Reconstruction – would also meet the project purpose and need, but it would also add through lanes to provide reserve capacity to meet future needs.
What are Alternatives 4a, 4b and 4c?
Three variations of Alternative 4 (a, b and c) are evaluated in the Alternatives Screening Report. Through most of the North Split interchange, Alternatives 4a, 4b and 4c are the same. They all provide a smaller overall footprint, improve safety at the worst crash locations and remove most of the bottlenecks that currently cause congestion. Alternatives 4a, 4b and 4c differ in how they connect with the Pennsylvania Street exit ramp and the Delaware Street entrance ramp on the west leg of the interchange.
Why focus on the Pennsylvania Street exit ramp and the Delaware Street entrance ramp?
The highest crash rate in the project area is at the Pennsylvania Street exit on the west leg of the interchange. I-65 traffic must cross the path of traffic coming from I-70 to reach the exit. This crossing movement is referred to as “weaving.” The second highest crash rate in the project area is at the Delaware Street entrance ramp, where entering traffic must cross all I-65 traffic to access I-70 eastbound, creating a second weaving area. Eliminating these weaving areas is essential to improve safety in the interchange. It would also remove two of the main bottlenecks that cause congestion.
How do Alternatives 4a, 4b and 4c vary on the west leg of the interchange?
Alternatives 4a, 4b and 4c eliminate the weaving areas on the west leg in three different ways. The configuration of these local ramp connections determines what connections can be made at these ramp locations (if any), as well as how much the interstate needs to be widened and how high retaining walls need to be to keep the project within existing right of way. In effect, Alternatives 4a, 4b and 4c provide a series of trade-offs between the number of available movements and the physical impact on the adjacent area. These trade-offs are summarized in the table below. Alternative 5 is included in the table to illustrate the effect of adding through lanes while serving all movements at the ramps.
West Leg Access and Impacts – Alternatives 4a, 4b, 4c and 5
What trade-offs are associated with the alternatives?
Based on the information provided in the table above, the trade-offs with the alternatives can be summarized in terms of ramp connections and the maximum height of retaining walls along the west leg of the interchange, as follows:
- Alternative 4a: Pennsylvania Street exit closed, Delaware Street entrance closed. No retaining walls
- Alternative 4b: Pennsylvania Street exit open to I-65 and I-70, Delaware Street entrance open to I-65 and I-70. 18-foot retaining wall north of I-65; 33-foot retaining wall south of I-65
- Alternative 4c: Pennsylvania Street exit open to I-65 only, Delaware Street entrance open to I-70 only, I-65 access to Ohio and Michigan streets eliminated. 11-f00t retaining wall north of I-65, 7-foot retaining wall south of I-65
- Alternative 5: Pennsylvania Street exit open to I-65 and I-70, Delaware Street entrance open to I-65 and I-70. 30-foot retaining wall north of I-65, 37-foot retaining wall south of I-65
Why was Alternative 4c chosen as the Preliminary Preferred Alternative?
Alternative 4c would meet the project purpose and need effectively by replacing deteriorated pavement and bridge infrastructure, improving safety at the highest crash locations and reducing traffic congestion by removing existing bottlenecks. Improvements would be made throughout the interchange, but a key area of improvement would be the west leg, where existing weaving areas create the greatest hazards and bottlenecks in the interchange.
Based on a review of the trade-offs between benefits and impacts of the alternatives, INDOT has determined that Alternative 4c would provide the best balance of meeting safety and mobility needs while minimizing impacts on adjacent neighborhoods. Subject to input from agencies, advisory committees and the public during the comment period of the Alternatives Screening Report, Alternative 4c will be the preliminary preferred alternative to be analyzed in detail in the EA.
If Alternative 4c is advanced as the preferred alternative in the EA, will additional measures be investigated to minimize impacts to surrounding neighborhoods?
As the NEPA process moves forward, the preliminary preferred alternative will be defined in greater detail and opportunities will be investigated to further reduce impacts, including the following:
- Options to adjust the steepness of the slopes or the location of the bottom of the slopes will be investigated to determine whether the retaining wall heights can be reduced or if the retaining walls can be eliminated entirely at some or all locations
- Aesthetic treatments will be investigated throughout the corridor in consultation with neighborhood representatives and consulting parties to improve neighborhood integration
- Local traffic impacts and connectivity across the corridor will be investigated and plans will be developed to minimize impacts and enhance opportunities or all modes of travel, including pedestrians and bicycles, as well as motor vehicles using the local roadway system
The project team will continue to work with the Community Advisory Committee (CAC) and others to enhance the North Split project and minimize community impacts as the project moves from the NEPA process to implementation.