Berkeley: Filtered Permeability Pioneer?

Since the mid-1960s, when the first traffic diverters were installed to protect the area around San Pablo Park, residents and pundits alike have dissed the concrete bollards that dot many of Berkeley’s neighborhoods. Drivers who find themselves redirected in concentric circles around their intended destination question the sanity of the traffic engineers responsible for their deployment. Neighbors living near the bollards say they’re unsightly and detract from the beauty of the neighborhood. In the mid-1970s, opponents successfully placed two separate initiatives on the ballot to have the bollards removed. Both measures failed. Lawsuits were later filed to remove the bollards, alleging they didn’t conform to CalTrans standards. The state legislature subsequently legalized all such diversion techniques.

In reality, traffic diversion has been quite effective in many of the neighborhoods where the bollards have been installed. The Claremont neighborhood is a prime example of this success. Traffic that used to spill into the neighborhood during peak commuter hours is now unable to penetrate the interior. Children can safely walk from their homes to Monkey Island Park without encountering commuters slicing frantically through the back streets to get from Claremont Blvd. to Derby St. At the same time, cyclists and pedestrians are able to pass through the barriers and therefore have unrestricted access to any part of the neighborhood.

Admittedly, the bollards are ugly as sin. Efforts to beautify them have achieved only lipstick-on-a-pig success. Some of the configurations make no sense and serve no purpose. Yet Berkeley appears to have been very much a visionary city as new strategies proposed by leading New Urbanism and Smart Growth experts emerge. The difference? Berkeley attempted to retrofit a street network originally optimized for autos and the new strategies build pedestrians, cyclists and mass transportation into the cityscape design. As a result, more attractive means of filtering traffic can be used.

A recent article by British transportation expert Steve Melia examines a design strategy called filtered permeability that, not unlike the bollards, promotes walking and cycling by making those forms of transportation more efficient, and therefore more attractive, than less sustainable options. To paraphrase Melia, if a street is designed for equal access by all forms of travel, people will often choose the most convenient mode of transportation (i.e. autos). However, if part of that street is restricted to autos, it becomes more convenient to walk or ride a bike. So bikes and pedestrians have greater permeability than autos, hence the term.