$58 million to relieve I‑680/SR‑4 bottleneck in Contra Costa County

The Interstate 680/State Route 4 Interchange Improvement Project, a long‑awaited upgrade that will untangle one of Contra Costa County’s most persistent traffic chokepoints, will receive $58 million from the California Transportation Commission (CTC).

Last month the CTC approved the funding for the next phase of the project. The new state dollars will be paired with approximately $160 million in Regional Measure 3 and Contra Costa’s Measure J transportation half-cent sales tax, enabling the Contra Costa Transportation Authority (CCTA) to begin construction next year with completion slated for the end of 2028.

MTC allocated the Regional Measure 3 monies toward the project. 

“This interchange is a critical bottleneck in Contra Costa County, and the project will enhance safety, reduce congestion, and improve operating efficiencies for all users — including the freight movement that keeps our economy moving,” said Tim Haile, Executive Director of CCTA.

State Route 4 is the primary east‑west link connecting Antioch, Bay Point, Pittsburg, and Brentwood with central Contra Costa County and the wider Bay Area, while Interstate 680 serves as the north‑south backbone through the county. The existing interchange forces drivers into a short, hazardous weave movement that contributes to collisions and backups.
The improvements will:

• Construct an elevated ramp that carry traffic directly between southbound I-680 and eastbound SR-4 to replace the existing tight loop ramp that currently causes the weave conflict.
• Extend the connector ramp from eastbound SR-4 to southbound I-680 to eliminate the weave from the Muir Road on-ramp.
• Add modern ramp metering system on the new connector to smooth merging onto the freeway and remove the tight loop ramp that currently causes the double‑weave conflict.

These upgrades will reduce travel times, boost safety, and cut greenhouse‑gas emissions by smoothing traffic flow and reducing idling. Final design for this phase is nearing completion.