State Route 710 (California)

State Route 710 (California) is a north–south state highway in the Los Angeles metropolitan area consisting of two discontinuous freeway segments in Los Angeles County. The corridor historically formed part of a planned longer freeway connecting the ports and industrial areas near Long Beach with the San Gabriel Valley, but a central unconstructed gap has left the route divided between a short stub in Pasadena/South Pasadena and a longer segment running from Alhambra to El Sereno and north to San Marino and Arcadia. The route has been the focus of extensive planning, political debates, and community activism involving entities such as Caltrans, the California Department of Transportation (Caltrans), the Metro, and city governments.

Route description

State Route 710 begins at an interchange with Interstate 10 (I‑10) in eastern Pasadena near Lake Avenue and runs north as an elevated freeway through parts of Pasadena, adjacent to neighborhoods and institutions including Pasadena City College, the California Institute of Technology, and near the Rose Parade route. North of the Pasadena segment a discontinuity occurs at the city limit with South Pasadena; the unbuilt section would otherwise continue through neighborhoods and business districts adjacent to the LA Metro A Line light rail corridor and under/near historic districts such as Old Pasadena. The northern constructed section resumes near Alhambra and proceeds north through or near cities including Alhambra, San Marino, South El Monte (adjacent), and Arcadia to its terminus at I‑210 in the foothills at the base of the San Gabriel Mountains. Along its alignment the freeway provides access to major arterials such as Huntington Drive, SR 19 (Lake Avenue), Atlantic Boulevard, and Mission Road, and is used by commuter traffic linking suburban nodes, freight routes to the Port of Long Beach, and regional connectors to freeways like I‑5 and I‑605.

History

The corridor originated as part of early 20th‑century plans for an arterial connecting Long Beach with the eastern San Gabriel Valley and was incorporated into the state highway system during expansions in the 1930s as Legislative Route 167. Postwar freeway planning in the 1940s and 1950s, influenced by agencies such as the California Division of Highways (predecessor to Caltrans) and regional planners associated with the SCAG, envisioned a continuous limited‑access highway. Construction of northern and southern segments occurred in phases during the 1950s through the 1970s, contemporaneous with the development of other major projects such as I‑10, I‑710, and the Arroyo Seco Parkway (SR 110). Opposition to the full construction emerged in the 1970s and 1980s from community groups and municipal governments in South Pasadena, Pasadena, and San Marino, citing impacts to historic districts, properties such as those within the California Institute of Technology area, and local environmental concerns tied to air quality overseen by agencies like the South Coast Air Quality Management District. Legal actions and ballot measures culminated in partial cancellations and a persistent unconstructed gap that remains a focal point for regional transportation planning, litigation, and ballot initiatives involving the Los Angeles County Board of Supervisors and local city councils.

Unconstructed gap and proposals

The central unconstructed gap between the southern Pasadena stub and the Alhambra/Arcadia segment has given rise to multiple proposals over decades. Options considered by Metro, Caltrans, and local governments have included completing the freeway tunnel or surface freeway, implementing an at‑grade boulevard conversion, constructing a deep bore tunnel similar to projects such as the Big Dig conceptually, or enhancing transit alternatives including an extension of the Metro A Line or a dedicated bus rapid transit corridor. Ballot measures and voter actions, including local initiatives in South Pasadena and countywide measures, have shifted policy away from full freeway completion and toward multimodal solutions. Engineering studies examined alignments that would interact with infrastructure such as the Los Angeles River, utilities owned by Southern California Edison, and rail right‑of‑way controlled by the Metrolink commuter rail operator. Environmental impact analyses under the California Environmental Quality Act and federal reviews under the National Environmental Policy Act have assessed air quality, noise, seismic safety given proximity to the San Andreas Fault system, and effects on historic districts like Old Pasadena. Advocacy coalitions, including neighborhood associations and environmental groups such as the Sierra Club, have opposed freeway completion; proponents including business coalitions and some freight stakeholders have argued for improved goods movement to the ports. In recent years, the focus has shifted toward interchange improvements, pedestrian and bicycle investments, and targeted congestion relief projects overseen by Caltrans District 7 and Metro's planning divisions.

Major intersections

The constructed portions of the route include interchanges with several principal arterials and freeways: the southern terminus at I‑10 in Pasadena; connections with SR‑110 via local interchange systems near the Arroyo Seco Parkway corridor; junctions with Huntington Drive in South Pasadena/San Marino vicinities; intersections serving Alhambra municipal streets and commercial zones; and the northern terminus at I‑210 in Arcadia. Additional ramps and access points link to county routes such as SR‑19 and major local connectors including Colorado Boulevard, Mission Road, and Atlantic Boulevard, shaping commuter flows to regional destinations like Downtown Los Angeles, San Gabriel, and the Port of Los Angeles complex.

Related transportation projects

Related projects influencing the corridor include Metro's systemwide plans for extensions of the A Line and improvements on the L Line corridors, freight investments connected to the Port of Long Beach and the Port of Los Angeles, and countywide initiatives such as the Measure R and Measure M funding programs. Infrastructure upgrades coordinated with LA Metro and Caltrans have addressed seismic retrofit needs similar to those undertaken on the Vincent Thomas Bridge and retrofit programs following guidelines from the AASHTO. Streetscape and complete streets proposals along the corridor draw on policies advanced by the Los Angeles County Bicycle Coalition and transit planning models used by agencies like the Federal Transit Administration. The corridor's future continues to be shaped by interactions among municipal planning departments in Pasadena, South Pasadena, Alhambra, Arcadia, regional planners at SCAG, and state authorities including Caltrans.

Category:State highways in California Category:Transportation in Los Angeles County, California