Early one morning in July 2008, a group of friends gathered on the Fletcher Drive Bridge near the Atwater neighborhood of Los Angeles. In workers’ vests and hard-hats, protected by orange cones and barriers made of sawhorses, and wielding brooms, stencils, and a professional lane-striping device, they went to work amidst the early-morning traffic over the L.A. River. In less than an hour, and for a few hundred dollars in materials, they painted a new bicycle lane. The plan’s originators were moved by a desperate lack of safe cycling routes across the bridges between the city’s downtown and its East and Northeast sides, and had been inspired by similar do-it-yourself streetscaping actions in Toronto. They had studied old city bike plans, researched official regulations and design standards, and practiced their lane-striping skills in a K-Mart parking lot. They even put up two professional road signs denoting the new lane, with small letters at the bottom of each attributing the work not to the DOT, but to “DIY.”

Actions such as these—unauthorized, highly local, largely anonymous, simple, impermanent, and often far from slick—may seem rather insignificant when considered individually, or in comparison with the broad strokes of formal planning and public infrastructure. And yet they are bold contributions to the very fabric of the city and quintessential elements of the phenomenon of spontaneous interventions that we are celebrating at the U.S. Pavilion.

While guerrilla bike lanes have found great popularity among cycling activists, the small-scale, do-it-yourself approach can be seen addressing issues throughout the built environment: a New Yorker removes corporate advertisements from bus stops and phone booths and replaces them with artwork; community members in Portland, Ore., “reclaim” their intersection with decoration, crosswalks, and streetscaping; a woman in New Orleans jack-hammers into the asphalt to plant saplings; a few friends in Pittsburgh plant and tend a road median near their homes.

These interventions are small, locally motivated, and focused from the start on specific problems, problems that the people behind the projects see as needing to be fixed. As such, the actions may be oneoff events: a square curb softened with cement, a handful of seeds strewn in a vacant lot, “sharrows” (a symbol depicting a bike and two chevrons) stenciled on a half-mile of boulevard. As with the guerrilla bike lane painters, these creators often remain anonymous, too, wanting their actions to speak for themselves. Certainly, some must appreciate the modicum of acclaim that their actions sometimes receive in the press, but they rarely parlay the efforts into wider recognition or financial gain. Others say that the best design interventions are those that don’t stand out at all, which allows them simply to be used and appreciated by the public they are intended for without drawing attention from authorities.

Despite their small size, these interventions make an impact. In taking design actions into their own hands, citizens not only directly affect the change they want to see but may inspire others to do the same, fostering the possibility of a ground-up, crowd-constructed city. Even if these interventions are removed by authorities, they suggest the sort of city that residents actually want to see, something that authorities occasionally even recognize.

In L.A., the Fletcher Drive Bridge bike lane didn’t last long. Though cyclists had been using the bridge regardless, and observers of the new lane reported cars and cyclists safely respecting it, the city worried it was unsafe and removed it in a matter of days. That same year, however, someone signposted a long stretch of 4th Street popular among cyclists as a “bicycle boulevard.” And in late 2009, other Angelenos stenciled bicycle sharrows in the city’s Highland Park neighborhood. A few months later, hundreds of community members worked overnight to wheatpaste thousands of “Pass with Care/Pase con Cuidado” signs at intersections across the city.

And today? The city’s plans and street marking formally acknowledge 4th Street as a major artery in an expanding cycling network. The Department of Transportation began laying official sharrows and better signage on L.A. streets in 2010. As for improving cycling access across the Los Angeles River, only one of the city’s 14 bridges has been identified for painted, on-street bike lanes. Guess which one it is?