Cyclists in San Francisco have been shown six designs by consulting engineer Arup for a 4.7km bike path over San Francisco Bay, from the island of Yerba Buena to the city proper. Â
The project has a special significance for Arup because one of its leading structural engineers died while cycling in the city 13 years ago.
We have the opportunity to create something really inspiring that could last 100 or 200 years. Adding a bike path to half of the Bay Bridge isn’t just a huge project. It’s three huge projects– Rafael Manzanarez, Arup lead bridge designer
The aim is to fill in a gap in the city’s cycle links. Now cyclists can pedal north from San Francisco over the Golden Gate bridge to Marin County, and vice-versa, but they cannot pedal east over the Oakland Bay bridge to Oakland and Berkeley.
Arup’s designs meet that need in in a variety of ways. One proposal is for a dramatic five-loop spiral that takes riders up 150ft from street level to the deck of the Oakland bridge (pictured).
Arup estimates that as many as 10,000 cyclists and pedestrians would use the path each day.
The main technical problem for the UK engineer is how to connect the 15ft wide path to the bridge without using welding, which the "old steel" of the Oakland Bridge would not be able to withstand.
Rich Coffin, Arup’s principal engineer, and Rafael Manzanarez, its lead bridge designer, gave a presentation to a meeting of cyclists in January where they outlined the possible solutions to the engineering problem, and discussed whether the cycle path would run along the north, south, or above the bridge, as well as where it would touch down in San Francisco and Yerba Buena.
One of the designs that Arup has shown San Franciscan cyclists (Arup)
Manzanarez told his audience: "We have the opportunity to create something really inspiring that could last 100 or 200 years." However, he added that the scheme presented serious engineering challenges. He said: "Adding a bike path to half of the Bay Bridge isn’t just a huge project. It’s three huge projects."
The main financial problem is how to build these huge projects for less than $300m, which is the budgetary ceiling. Arup is working with city officials to find a design that can be erected for the money available. The cost of construction may be met by charging a toll on users.
Cyclist looking forward to making the 45 minute journey between San Francisco and Oakland will have to be patient, however. The earliest date envisaged for completing the scheme is 2025.
The need to make cycling safer in San Francisco has a special significance for Arup. In 2003, Tony Fitzpatrick, the chairman of the London-based firm’s American division and one of the world’s leading structural engineers, died in a traffic accident while cycling in the city.
Top photograph: The Oakland Bay bridge, to which the new cycle path must somehow attach (Frank Schulenburg/Wikimedia Commons)