work on the western highrise span was bid in october 1964 and commenced in 1965. it crosses a shipping channel, with an orthotropic main span that is long (at the time, the longest girder span in the united states) and has a vertical clearance of . the main span is flanked by two orthotropic back spans which are each long, and there are seven orthotropic side spans on the approach to each back span. each of these side spans are long. although these spans appear to be formed from continuous box girders, they consist of alternating anchor spans and suspended spans. anchor spans rest on top of two adjacent piers and cantilever over each side slightly, and suspended spans are hung between the ends of two adjacent anchor spans. there are an additional nine steel spans carrying a concrete deck on the san mateo side of the highrise, and ten steel spans carrying a concrete deck on the hayward side, ranging from . the bridge carries about 93,000 cars and other vehicles on a typical day, almost double its original projected design capacity of 50,000 vehicles per day.