Since 1992, cyclists riding in San Francisco's monthly Critical Mass bicycle rides had used the "corking" technique at street intersections to block rush-hour cross-traffic. In 1997, Brown approved San Francisco Police Department Chief Fred Lau's plan to crack down on the rides, calling them "a terrible demonstration of intolerance" and "an incredible display of arrogance." After arrests were made when a Critical Mass event became violent, Brown said, "I think we ought to confiscate their bicycles" and "a little jail time" would teach Critical Mass riders a lesson. On the night of the July 25, 1997, ride, 115 riders were arrested for unlawful assembly, jailed, and had their bicycles confiscated. By 2002, Brown and the city's relations with Critical Mass had changed. On the 10th anniversary of Critical Mass on September 27, 2002, the city officially closed down four blocks to automobile traffic for the annual Car-Free Day Street Fair. Brown said of the event, "I'm delighted. A new tradition has been born in our city."