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Westbound Auxiliary Lane Addition on SR-91 from the SR-55 Connector to the Tustin Avenue On-Ramp 

Anaheim, CA

Client: OCTA


Westbound Auxiliary Lane Addition on SR-91 from the SR-55 Connector to the Tustin Avenue On-Ramp


As part of the Caltrans District 12 and OCTA process to eliminate freeway chokepoints, OCTA hired Civil Works Engineer's staff to prepare a Project Study Report for the addition of an auxiliary lane from the northbound to westbound SR-55 to SR-91 connector through the westbound Tustin Avenue interchange. This section of the freeway crosses over the Santa Ana River. The two-lane existing connector merges to one-lane and the resultant auxiliary lane currently is a forced drop lane at the Tustin Avenue off-ramp. Therefore, all connector traffic intending to access westbound SR-91 must merge onto the mainline and weave with Tustin Avenue off-ramp traffic. This section of freeway is plagued with congestion and weaving, poor levels of service, and higher than average accident rates.

The project identified three alternatives for study. Alternative 1 is the no build. Alternative 2 will provide an auxiliary lane from the connector terminus, therefore not requiring all connector traffic to merge onto the mainline and still providing one lane which drops at the Tustin Avenue off-ramp, all the way until the Tustin Avenue on-ramp merges into it. The new lane would then connect with the existing auxiliary lane between the westbound Tustin Avenue on-ramp and the westbound SR-91 to northbound SR-57 connector. An option of Alternative 2 is to relocate the diverge of the Tustin Avenue off-ramp to the east, prior to the connector merge. It would then parallel the connector and the freeway and join back to the mainline. This would serve to significantly reduce the weaving between the connector and off-ramp traffic. Alternative 3 proposes to braid the connector and the off-ramp. In this alternative, the Tustin Avenue off-ramp would be relocated further east and the connector merge would be relocated further west. Just west of the river crossing, the off-ramp would be grade separated above the connector. A slip ramp from the connector would be provided to access the off-ramp prior to it's merge with the mainline.

Project involved the examination of several structures including replacement of the Riverdale Avenue overcrossing, tie back walls at the Riverdale Avenue overcrossing, replacement of the Tustin Avenue 
overcrossing, widening of the Santa Ana River bridge, a new off-ramp structure crossing the river, and a grade separation structure for the braid alternative. Project components included traffic analysis and forecasting, preliminary geotechnical assessment, review of the river freeboard, initial site assessment, fact sheets, storm water data report, utility review, right of way review/data sheet, traffic management plan review, and preparation of the PSR.  


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