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Elements of Sustainable Transportation

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Great Streets


March 9, 2001 . . .

A highlight of the Local Government Commission's recent "smart growth" conference, "Redefining Community", held in San Diego, was a talk by University of California, Berkeley Professor Alan Jacobs entitled "Great Streets." The author of a beautiful coffee-table book of the same name, Jacobs summarized his lifetime of direct observation of what makes a street and its intersections great -- or not.

"It's no big mystery. The best streets are comfortable to walk along with leisure and safety. They are streets for both pedestrians and drivers. They have definition, a sense of enclosure with their buildings; distinct ends and beginnings, usually with trees. Trees, while not required, can do more than anything else and provide the biggest bang for the buck if you do them right. The key point again, is great streets are where pedestrians and drivers get along together."

Jacobs urges that cities "copy the good examples." He observes, "For at least 60 years, city engineers have been anti-urban, anti-pedestrian and anti-mixed use. As a philosophy, they moved to segregate uses and then they moved to segregate people and cars under the guise of safety, with an emphasis on size -- wider, larger -- and this is anti-pedestrian. Existing standards are not even based on research, they're mostly based on queuing problems. We're told by traffic engineers that intersections where pedestrians and drivers get along together are dangerous, mostly because of the multiple turning points and complex interactions required. But this is the exact opposite of what real research and observation of existing great intersections tell us."

He related the story of two parallel major boulevards in Northern California. One was dominated by the signal and separation approach. The other had a clear pedestrian realm, narrower lanes, separation of local traffic, and more complex intersections. The former was barren of street life, with higher accident rates. The latter was alive with the vibrancy of place. And the engineering bottom line: they carried the same volume of traffic.

Jacobs has studied great streets in amazing detail. He says, "great streets have 9- to 10-foot lanes and 7- to 8-foot parking maximum, if they have parking. Though present more than not, parking in great amounts is not a characteristic of great streets. At great intersections we've found that every movement is often possible.

"We've counted up to 50 possible conflict points -- as compared to the 16 preferred by most traffic engineers in a normal four-way intersection. The reason great intersections work is because of the creation of a pedestrian realm where the cars know this. When streets become unsafe, it is almost always when the pedestrian realm does not exist. One other point, property values on narrower streets are higher than for the same houses on wider streets."

Sadly, he laments, "most of the great intersections and streets I've observed could not be built today. But based on real accident records, they are not more dangerous than currently 'normally designed' streets and intersections -- and have similar if not higher throughput."

What are the conclusions for cities like San Diego -- on the verge of outgrowing both the design and capacity of our existing streets?

The region's pedestrian advocacy group, Walk San Diego, has a long list of invitations from frustrated neighborhood groups who are in near revolt over the way the city's streets are designed. In the mid-1990s the City Council appointed a street design manual user Group to consider improvements. The group recommended changes to restore the "balance of power" between drivers and other users of the street. Unfortunately, these recommendations, received in 1998, were never moved forward. Today, as the city contemplates what it will take to implement its "city of villages" concept, it should return to those recommendations -- adopt those and then look for other improvements.

Where to start? The city has been provided with a copy of "Street Design Guidelines for Healthy Neighborhoods," by Dan Burden. This manual was produced by the same, stubbornly optimistic Local Government Commission. It is one of the few manuals based upon direct measurements of streets that work and don't work -- not on abstract engineering concepts disconnected from other community factors.

Burden's text explains that a major limit of modern traffic engineering, as it is practiced, is the propensity to optimize one variable to the detriment of others. Auto traffic throughput has been so dominant a factor that other issues important to community livability have been ignored, forcing potential pedestrians and transit riders into their cars for even short trips. Without great streets -- designed for pedestrian safety -- we can never achieve great transit. Not surprisingly, traffic continues to worsen.

Another lesson here is that intersections must not be designed cookbook-style. They either provide sufficient capacity for all users by their design or they become terrible bottlenecks or danger zones. The city has moved to install electronic ticketing devices at problem intersections -- which is basically equivalent to a financially punitive ramp meter. I would bet that each of these sites is really a failure of our cities' street and intersection design versus the growth permitted. At the very least, fees from those intersections should be earmarked to redesign and ultimately rebuild them to transform these mini-police states back into functioning, vibrant places where through traffic can get through and local traffic includes pedestrians, bicycles and daily life on what could become great streets.

Without great streets and intersections, we cannot be a great city, much less one that can absorb forecasted growth without taking more of us hostage -- on a dangerous sidewalk or in a traffic jam.

    Carolyn Chase is editor of the San Diego Earth Times and chair of the mayor's citizen's environmental advisory board. E-mail her at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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