A neighborhood bikeway should have fewer cars, not more of them

November 10, 2017

If you ask Google Maps how to bike north or south through San Francisco’s Richmond neighborhood, the streets it recommends for biking are marked in green:

That’s Golden Gate Park to the south and the Presidio to the north — two of the country’s most famous and beautiful public parks. If you’re an ordinary person who wants to bike from one to the other, your best bets are busy Arguello Boulevard, with its unprotected door-zone bike lanes, or 8th Avenue.

8th Avenue is flat. It’s continuous. It has traffic signals at Geary, Clement and California, making its big streets easy to cross. It connects to two supermarkets and the heart of the neighborhood commercial district.

It’s a perfect bike route, except for one thing: those things all make it a perfect street to drive on, too.

Here’s a chart of weekday auto traffic counts on the streets through this area. Guess which street is the officially designated bikeway:

This is a familiar Catch-22 for designated side-street bike routes around the country: If the route goes where you want to go, it’s probably got too many cars to be a low-stress bike route. If it’s pleasantly low-traffic, it probably doesn’t go where you need.

This is the dilemma the San Francisco Municipal Transportation Agency is setting out to solve. The city plans to turn this stretch of 8th Avenue into its first “neighborway,” the local term for a neighborhood bikeway. The key change: new traffic diverters at two cross streets, Anza and Balboa, that force people in cars to turn left or right off of 8th rather than continuing straight.


Image: San Francisco Municipal Transportation Agency.

Local auto traffic will still be able to reach every point on every street, but the diverters should make it impossible for people in cars to use 8th Avenue as a cut-through street:


A semi-diverter like those planned for 8th Avenue in San Francisco. Image: NACTO.

And according to SFMTA’s calculations, those diverters will turn the 8th Avenue neighborway from the highest-traffic local street in this neighborhood to one of the two least stressful, without pushing the cars onto any other local street in particular:


Image: San Francisco Municipal Transportation Agency.

To many people accustomed to driving on 8th, of course, the new diverters may be annoying. And most of the cars diverted from 8th will wind up on someone else’s street.

But the beautiful thing about building neighborhood bikeways into a citywide network is that it’s not a zero-sum game: reducing auto traffic on one street doesn’t necessarily increase auto traffic on another street.

If you use diverters to carefully create a connected network of pleasant bikeways, people don’t get into cars as often in the first place. That’s a win for every single San Franciscan — and the rest of the world, too.

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