Review Preliminary Design Alternatives

How were the alternatives identified?

A collaborative process was used to develop three preliminary design alternatives for further community feedback. The process of developing the alternatives included three primary steps:

  1. The corridor was assessed and evaluated. Future growth in the region was considered to understand existing and future mobility and safety issues along the corridor. A technical analysis was performed in collaboration with the City of Kelso, and WSDOT. The community provided feedback through stakeholder interviews, surveys, and a public open house. These efforts helped to identify a range of issues to address.
  2. A long list of potential solutions was identified to address the issues. Nearly 50 solutions were identified, focusing on all modes of travel ranging from small to complex improvements.
  3. The list of solutions was refined based on which ones addressed the project objectives, and were shown to be feasible. The solutions that best addressed the project objectives were grouped into three preliminary design alternatives for further community feedback.

The graphic below shows the process used to develop the design alternatives.

Developing the Design Alternatives

Step 1

graphic representing analysis

Conduct Analysis and Outreach

Assessment of
existing issues

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Analysis of future needs

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Staff/agency discussions

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Stakeholder/​public input

Step 2

graphic representing solution list

Prepare List of Potential Solutions

Roadways/​Intersections

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Pedestrian/​Bicycle

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Safety

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Transit

Step 3

graphic representing evaluation

Screen and Evaluate Solutions

Does the solution meet the project objectives?

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Are there feasibility issues or concerns?

 

Alt 1

Alt 2

Alt 3

Preliminary Design Alternatives

Overview of Design Alternatives

Alternative 1: Traffic Signal and Channelization Enhancements

This alternative proposes to improve mobility and safety along the corridor through signal upgrades at three locations (I-5 Northbound Ramps, I-5 Southbound Ramps, S Kelso Drive/N Minor Road) and channelization improvements.

Plan view drawing of concept 1

Graphic showing traffic signal enhancements along Allen Street at the southbound I-5 ramps, northbound I-5 ramps, and S Kelso Drive/N Minor Road intersections.

Click image to enlarge

This alternative includes the following improvements:

  • Improved signal synchronization/coordination using Intelligent Transportation Systems (ITS) equipment
  • Enhanced pedestrian and bicycle facilities
  • Improved lighting, landscaping, and stormwater facilities
  • Channelization improvements to increase turn-lane capacity along the corridor
    • Lengthen eastbound and westbound left-turn lanes between the I-5 Ramps
    • Install westbound right-turn lane at I-5 Northbound Ramps
    • Install 2nd northbound left-turn lane along S Kelso Drive
    • Install dedicated southbound left-turn lane along N Minor Road
  • Access control restrictions (right-in/right-out movements)
    • Allen Street at Holly Street
    • S Kelso Drive at commercial driveways

Alternative 2: Single-Point Urban Interchange

This alternative proposes to improve mobility and safety along the corridor by installing a single-point urban interchange (SPUI). A SPUI would control movements at the I-5 ramps using a single traffic signal.

Plan view drawing of concept 2

Graphic showing a Single-Point Urban Interchange at the Allen Street and I-5 ramps intersections to be controlled by a single traffic signal.

Click image to enlarge

This alternative includes the following improvements:

  • Replace the two I-5 Ramp intersections with a SPUI intersection
  • S Kelso Drive/N Minor Road intersection controlled by its own, upgraded traffic signal
  • Channelization improvements to increase turn-lane length along the corridor
    • Install 2nd northbound left-turn lane along S Kelso Drive
    • Install dedicated southbound left-turn lane along N Minor Road
  • Enhanced pedestrian and bicycle facilities
  • Improved lighting, landscaping, and stormwater facilities
  • Access control restrictions (right-in/right-out movements)
    • Allen Street at Holly Street
    • S Kelso Drive at commercial driveways

Alternative 3: Roundabouts

This alternative proposes to improve operations along the corridor by installing multi-lane roundabouts at three intersections (I-5 Northbound Ramps, I-5 Southbound Ramps, S Kelso Drive/N Minor Road). This alternative would most likely require widening the roadway.

Plan view drawing of concept 3

Graphic showing multi-lane roundabouts along Allen Street at the southbound I-5 Ramps, northbound I-5 ramps, and S Kelso Drive/N Minor Road intersections.

Click image to enlarge

This alternative includes the following improvements:

  • Install roundabouts at intersections along the corridor
    • I-5 Ramps: singular, connected (“dog-bone”) roundabout controlling both intersections
    • S Kelso Drive/N Minor Road: independent roundabout
  • Enhanced pedestrian and bicycle facilities
  • Improved lighting, landscaping, and stormwater facilities
  • Access control restrictions (right-in/right-out movements)
    • Allen Street at Holly Street
    • S Kelso Drive at commercial driveways