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1-5:Aurora Donald Interchange(Exit 278) Interchange Area Management Plan for Marion County Approval ODOTKN19062 Oregon Department of Transportation—Region 2 ultimately selecting the Diverging Diamond Interchange (DDI) as the Preferred Alternative based on performance and public and stakeholder feedback. Phasing of the DDI Preferred Alternative is needed to accommodate funding allocated in the Keep Oregon Moving Act.This funding represents a substantial down payment toward implementing the Preferred Alternative, but would not cover the full cost of the interchange.As a result, an initial Phase 1 project was developed. The remaining improvements to complete the Preferred Alternative comprise Phase 2 of the Project that would be implemented when funding becomes available in the future. The DDI Preferred Alternative is also known as a double crossover diamond interchange. In a DDI interchange configuration,traffic on Ehlen Road crosses to the opposite (left) side of the road while within the interchange (i.e., between the ramp intersection traffic signals). Dual traffic signals at the ramp intersections control the movement of traffic during this crossover maneuver. Upon reaching the second traffic signal,vehicles are returned to driving on the right side of the road.The DDI allows signalized ramp intersections on Ehlen Road to operate in a more efficient manner, as two-phase traffic signals.The DDI will improve safety because there are no left turns across opposing traffic and most turning movements are controlled by signals. Another safety and traffic operation benefit is that left and right turns can occur simultaneously. The DDI Preferred Alternative consists of the following Phase 1 and Phase 2 interchange improvements (see Figure 5-3). Phase 1 improvements are noted in bold. • Construct one new I-5 bridge to carry both north-and southbound traffic over Ehlen Road. • Reconstruct the 1-5 travel lanes to match the new I-5 bridge. • Realign 1-5 southbound lanes east,into the median,to align with the new bridge structure. • Lengthen,widen, and signalize northbound and southbound off-ramps. • Lengthen, widen, and signalize northbound and southbound on-ramps. • Construct a four-lane cross section on Ehlen Road, between the northbound and southbound 1-5 ramps,with left-turn lanes to access the 1-5 on-ramps and one through lane in each direction. • Realign Ehlen Road with a wider cross section under I-5 to include new signalized intersections located at the northbound and southbound ramp intersections and two lanes in each direction with bike and pedestrian facilities. • Realign Bents Road to align with Bents Court at existing Ehlen Road. • Realign Ehlen Road,west of 1-5, to the north and construct a new Ehlen Road/Bents Road intersection. • Realign Dolores Way to create a new intersection farther east with Ehlen Road. The estimated construction cost of Phase 1 is$50 million, and the estimated cost of Phase 2 is $29 million. July 2020 274-3012-031 ES-3