DATE: February 23, 2021
TO: Mayor and City Council
FROM: Director of Public Works
SUBJECT
I-880/Winton Ave and I-880/A Street Interchange Improvement Project: Select Preferred Alternative for the A Street Improvements to Present to Alameda County Transportation Commission for the I-880/Winton Ave and I-880/A Street Interchange Improvement Project
RECOMMENDATION
That Council reviews this report and selects a preferred project alternative for the A Street Improvements to present to Alameda County Transportation Commission (Alameda CTC) to move forward to the environmental document project phase.
SUMMARY
The City, in partnership with Alameda CTC, the implementing agency, and the California Department of Transportation (Caltrans) propose to provide interchange improvements at the Winton Avenue and A Street interchanges along the I-880 corridor.
There are several alternatives proposed to add an auxiliary lane on I-880 in both directions between the Winton Avenue and A Street interchanges, along with interchange improvements. After a cooperative evaluation with the Project Development Team, Caltrans, Alameda CTC, and City staff, the project team is proposing Mainline improvements to the Caltrans freeway right-of-way, one improvement scenario on Winton Avenue (Alternative W2) and three improvement alternatives (Alternatives A1, A2, and A3) on A Street as shown on Attachment III. All proposed alternatives are compared to the no-build scenario or existing condition in order to measure the impacts of each alternative. Staff is only seeking direction from Council on the three A Street alternatives since the project team has already narrowed down the proposed improvements for the Mainline and Winton Avenue areas. The following provides a summary of the Mainline, Winton Avenue, and three A Street alternatives:
Mainline Improvements. Mainline improvements would include restriping of the existing outside shoulder of I-880 along the I-880 mainline between the I-880/Winton Avenue and I -880/A Street interchanges to provide one auxiliary lane in each direction.
Winton Avenue Improvements. Alternative W2 proposes to convert the existing I-880/Winton Avenue Interchange from a full clover leaf to a partial clover leaf configuration. Partial clover leaf (Par-Clove) interchanges provide better traffic operations with minimum impact to right-of-way and environmental.
A Street Improvement Alternatives. The following provides a summary of each of the three A Street improvement alternatives at I-880/A Street interchange:
• Alternative A1 would modify the interchange ramp terminals from a signal control to a roundabout control.
• Alternative A2 includes removal of the existing sidewalks next to the travel lanes and restriping A Street to provide separate turn lanes for ramp turning movements in both directions. This scenario would provide six lanes under the existing A Street overcrossing.
• Alternative A3 includes removal of the existing sidewalks next to the travel lanes and widening existing A Street travel lanes while maintaining the existing five lane configuration under the A street overcrossing.
An analysis of performance measures indicates that Alternative A1 has higher safety
benefits, but higher delay and initial capital costs compared to the other alternatives. The roundabout design is very challenging as it increases the number of conflict points for non-motorized users, pedestrians, and bicyclists, and especially those with disabilities. It will present unique challenges to safety and accessibility concerns and it is not a community preferred alternative. Alternative A2 improves safety when compared to the no-build alternative and provides better traffic operations compared to the other alternatives. Alternative A3 is comparable to the no-build alternative in delays and also improves safety by providing better pedestrian and bicycle facilities.
Staff’s recommended alternative is Alternative A2 because it improves safety, improves pedestrian and bicycle connectivity, minimizes right-of-way impacts, has community support, is the least costly in terms of construction, and has the lowest post-implementation traffic operations impacts in terms of delay. All of which meet the Purpose and Need of the project. Alternative A3 is staff’s second preferred alternative for similar reasons, although future traffic operations will not be as improved under this alternative when compared to Alterative A2.
Staff requests that Council selects a preferred alternative for the A Street interchange based on the information provided within this report and the accompanying presentation.
ATTACHMENTS
Attachment I Staff Report
Attachment II Alternatives