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Located in the heart of the region’s freeway network, the San Gabriel River Freeway, or I-605 as it is more commonly known, is in need of an overhaul to improve freeway capacity and operational conditions. The I-605 serves as one of the few major north-south interstate freeways in the greater Los Angeles Area of Southern California, running roughly 27 miles from the coast in Seal Beach, at its most southerly point, to the foothills in Irwindale/Duarte in the north, where it connects to Interstate 210. The successful flow of traffic, free of congestion, along the project corridor is vital to local circulation and connectivity and to interstate commerce traveling inland from the ports.

The I-605 is a popular connector for public transit riders. It provides access for east-west travelers that use the Metro Green Line light-rail service serving the Norwalk Station at the I-105. The project corridor is also the travel path of the Metro Express Bus Line 577 running between I-10 and I-105. In addition, it provides a primary connection to the I-10, serving westbound Metro Silver Line riders at the El Monte station. Moreover, a number of Foothill Transit Commuter Express Lines run from the I-10 to SR-60 by way of the I-605.

Unfortunately, the freeway has gone without major system-wide improvements for roughly 50 years, since the construction of the first segment, Interstate 405 (I-405) to State Route 60 (SR-60), dating back to 1964 and the later portion completing construction in 1971. The I-605 features four general purpose/mixed-flow lanes and one HOV lane (2+ passengers) in both the northbound and southbound directions, and throughout most of the route. Presently, the stretch of freeway defined as the project limits include four 11-foot lanes with 2-foot wide median shoulder and one 12-foot HOV lane with a 1-foot wide HOV buffer. These conditions require change in order to meet the growing traffic demands of Southern California.

In March 2013, the SR-91/I-605/I-405 Congestion Hot Spots Feasibility Report (Feasibility Report) was prepared to assess the need for improvements to the corridor (Los Angeles County Metropolitan Transportation Authority and Gateway Cities Council of Governments, 2013), which revealed deficiencies in design, capacity, and operations that required action to reduce and manage congestion, and accommodate a forecasted increase in traffic volumes. In January 2017, Metro approved the Countywide ExpressLanes Strategic Plan. This plan establishes a vision for a system of the express lanes throughout Los Angeles County.  Express lanes will provide travelers with a seamless network of transportation options in congested freeway corridors.