Seattle’s Transportation Department didn’t have immediate plans to install any kind of buffer between car and bicycle lanes on Cherry Street when a guerrilla group of bicycle advocates decided in April to do it themselves.

Under the cloak of anonymity, a group calling itself “Reasonably Polite Seattleites” used temporary adhesive to place flexible plastic pylons between the busy, steep lanes on Cherry Street underneath Interstate 5.

“We wish we didn’t have to spend our own money on common-sense, unobtrusive traffic calming treatments, and risk arrest installing them, in order to feel safe riding in this city,” one of the advocates wrote to the city.

Though the city initially removed the posts, it has now spent about $20,000 to make the group’s wishes a reality.

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This past Sunday, city workers finished installing the first bicycle-lane buffer of its kind in the city with about 30 flexible posts on Cherry Street and Seventh Avenue. Workers narrowed the vehicle lane by 1 foot to create a buffer for the posts, said city engineer Dongho Chang. They even designated a left-turn box for bicyclists marked with a green, slip-resistant material and got rid of six parking spaces to make way for the new bicycle lanes put down on Seventh Avenue and Marion Street.

The city’s reaction less than four months after the rogue operation raises an inevitable question: Should anybody desiring a similar project think breaking the law might be worth it if it grabs the city’s attention?

According to the office of Mayor Mike McGinn — who is once again running for mayor as a staunch bicycle advocate himself — the answer is no.

“It’s a case-by-case basis thing — we don’t encourage people to put out traffic control devices on their
own,” said mayor’s office spokesman Robert Cruickshank.

Chang said there already had been plans to experiment with that kind of lane buffer. The group’s project just accelerated McGinn’s and transportation director Peter Hahn’s interest in seeing it installed, he said.

A day or two after the group’s buffer went up, Chang said, Hahn and McGinn asked him whether it would be possible to create an up-to-code version of the same kind of buffer in the area. Chang said he thought it was and decided to move forward with the pilot project.

“We want to see what kind of longevity it has and we want to hear from riders, what their feedback on it is,” Chang said.

Guerrilla pedestrian- and bicycle-safety advocates have also been active in Tacoma, where they’ve painted their own crosswalks and bicycle lanes on streets in at least six locations, said Josh Diekmann, a transportation engineer for the city of Tacoma. Because those advocates did not use removable materials and they did not meet city safety guidelines, the city spent about $1,000 at each location to remove paint.

Diekmann says the actions have not shifted the city’s project priorities.

“We look at our priorities in a wider context,” Diekmann said. “It takes some time to get some of these projects programmed and a lot of community input.”

Alexa Vaughn: 206-464-2515 or avaughn@seattletimes.com. On Twitter @AlexaVaughn.