Isabel, which is officially designated as State Route 84, provides a key link to Vineyard Avenue in Pleasanton and is a major traffic artery between Interstates 580 and 680.
The four-lane roadway has largely been rebuilt and widened from I-580 east to Jack London Boulevard just past the Livermore Airport, where it narrows to two lanes. A truck-passing lane on both sides of the route over Pigeon Pass has helped to reduce long delays in that section, but it could be years before the full planned four-lane expressway is completed.
Along with opening the Isabel Avenue interchange, Caltrans also closed the westbound I-580 Portola Avenue on-ramp. The eastbound I-580 off-ramp to Portola was closed several months ago.
These closures were necessary, Caltrans said, in order to connect Portola Avenue south of I-580 with the new Portola Avenue overcrossing, and the city of Livermore's extension of Portola north of I-580. For more information, call (510) 286-5445.