Interstate 605 (I‑605) is a north‑south auxiliary Interstate Highway in the U.S. state of California. Commonly referred to as the San Gabriel River Freeway, it serves the eastern suburbs of the Greater Los Angeles area, running parallel to the San Gabriel River and the Interstate 5 corridor.
Route description
I‑605 extends for approximately 27 mi (43 km) from its southern terminus at Interstate 405 in Seal Beach, Orange County, to its northern terminus at Interstate 210 in Duarte, Los Angeles County. The highway traverses four counties: Orange, Los Angeles, Riverside, and a small segment of San Bernardino. It generally follows the course of the San Gabriel River, providing a bypass for traffic between the coastal freeways (I‑405/I‑5) and the inland freeways (I‑15/I‑210). Major interchanges include connections with:
- Interstate 5 in Santa Ana
- State Route 91 in Cerritos
- State Route 60 in Whittier
- State Route 57 in South Cerritos and Hacienda Heights
- Interstate 10 in West Covina
- State Route 210 in Duarte
The roadway consists largely of a six‑lane (three lanes each direction) divided freeway, with portions expanded to eight lanes in higher‑traffic segments. It is equipped with standard Interstate safety features, including concrete barriers, illuminated guide signs, and extensive ramp metering.
History
The concept for an auxiliary route paralleling the San Gabriel River originated in the 1950s as part of the national Interstate Highway System planning. Construction began in the early 1960s, with the first segment opening between I‑405 and SR 60 in 1965. Subsequent extensions were completed throughout the 1970s, culminating in the final connection to I‑210 in 1979, at which point the highway was officially designated as Interstate 605. The route number follows the conventional numbering scheme for auxiliary Interstates, where a three‑digit number beginning with an even digit (6) indicates a bypass or beltway of its primary route (I‑5).
Traffic and usage
I‑605 functions as a major commuter corridor, handling an average daily traffic volume of roughly 150,000 vehicles on its busiest sections near the SR 57 interchange (as of 2022). The freeway also serves freight movement, providing an alternative route for trucks traveling between the ports of Los Angeles/Long Beach and inland distribution centers.
Future developments
The California Department of Transportation (Caltrans) has undertaken several improvement projects along I‑605, including ramp metering upgrades, lane widening in the Whittier corridor, and the installation of high‑occupancy toll (HOT) lanes. Environmental assessments are ongoing for potential extensions of the HOT lane system north of the SR 210 interchange.
Major intersections
| Milepost | Destination | Notes |
|---|---|---|
| 0.00 | I‑405 – Santa Ana, Newport Beach | Southern terminus |
| 5.5 | SR 91 – Artesia, Buena Park | |
| 7.8 | SR 60 – Pomona, Riverside | |
| 12.2 | SR 57 – Whittier, Hacienda Heights | |
| 18.9 | I‑10 – Los Angeles, Redlands | |
| 27.0 | I‑210 – Pasadena, San Dimas | Northern terminus |
References
- California Department of Transportation, “Interstate 605 Corridor Study,” 2021.
- Federal Highway Administration, “National Highway System: Interstate 605,” accessed 2023.
- Los Angeles Times, “I‑605 Expansion Plans Approved,” March 15 2022.
Note: All data reflect information available up to September 2023.