Traffic flows along Highway 24 at the Caldecott tunnel, were construction continues on the fourth bore of the tunnel seen here from the Oakland, Calif. side, on Friday, Aug 6, 2010. Caltrans contractors will use one of the world's largest roadheaders: a 130-ton, 54-foot-long and 14-foot-tall excavation device to carve out the new tunnel starting Monday.(Anda Chu/Staff)