State Route 57 (SR-57) is a major north-south freeway that connects Orange County with Riverside and San Bernardino Counties. State Route 60 (SR-60) is a primary link between Los Angeles and Riverside Counties, and a vital east-west route in the multi-modal transportation network in Southern California. The two freeways merge into a shared alignment for approximately a two-mile stretch known as the 57/60 Confluence.

The San Gabriel Valley Council of Governments (SGVCOG) estimated that 356,000 vehicles travel the 57/60 Confluence every day, with 26,000 of those being trucks carrying goods to warehouses. During the morning and the afternoon rush hours, peak traffic generally lasts for three to four hours on a typical weekday with an hourly volume of approximately 8,900 westbound vehicles and 9,400 eastbound vehicles traveling on six lanes of freeway.

Caltrans has identified the 57/60 Confluence as one of the five most congested segments within Caltrans District 7, which encompasses Los Angeles County and Ventura County. The 2037 traffic forecast indicates a 16% increase in traffic volumes on the two freeways.

The American Transportation Research Institute ranked this freight bottleneck as No. 7 in the nation and No. 1 for freight delays and truck accidents in California. Heavy freight traffic, trucks originating from the L.A. ports, make up an average volume of 8% to 10% during the peak hours.

The new eastbound 60-Grand Avenue/Northbound 57 separation bridge will be used exclusively by eastbound SR-60 commuters exiting Grand Avenue.

The Grand Avenue Interchange is located at about the midpoint in the 57/60 Confluence. With the weaving conflicts between traffic to and from the Grand Avenue Interchange and the two freeways, commuters experience long delays during both the morning and afternoon commutes.

Pictured here is the new Grand Avenue bridge that will be constructed with reconfigured on- and off-ramps.

The 57/60 Confluence improvements will:

  • Construct an eastbound on-ramp bypass lane from SR-60;
  • Construct a new eastbound general-purpose lane;
  • Reconfigure the Grand Avenue westbound on-ramp and the eastbound on- and off-ramps;
  • Widen Grand Avenue and reconstruct the Grand Avenue bridge overcrossing;
  • Construct an eastbound SR-60 off-ramp bypass from the northbound SR-57 split; and
  • Reconstruct the eastbound SR-60 Diamond Bar Boulevard on-ramp.

The new eastbound SR-60 bypass bridge over Diamond Bar Boulevard will be utilized by eastbound SR-60 commuters.

The San Gabriel Valley Council of Governments awarded the $267-million contract to Skanska for the SR 57/60 Confluence Project, with work beginning in July of this year. Targeted completion is July 2028.

More than 45,000 cubic yards of concrete is going into the project. The concrete that’s being removed in the process of rehabilitating the pavement will be recycled; ground up and used as base and structural backfill. Skanska will mobilize a crusher on site to more efficiently accomplish this and reduce the GHG emissions by eliminating the extra truck transport mileage.

Challenges include shallow groundwater around the project and soils requiring mitigation. To tackle the soil and groundwater issue, surcharges are being constructed, which then require 90 to 180 days for settlement. Supporting piles for the bridge structures will be driven 140 feet deep, and for the retaining structures, 30 to 50 feet deep.