SAN FRANCISCO — Hundreds of defiant bicyclists lined up single file here in July to protest, halting car traffic in a one-mile zigzag of streets known as the Wiggle that is popular among riders. Motorists honked and heckled during their stalled evening commute, as cyclists crept along to make their point: that they want the common practice of treating stop signs as yield signs — rolling through them slowly and coming to a stop only if necessary — to be legalized, for practical reasons.

Law enforcement officials had threatened to crack down on cyclists who failed to stop at signs, and the Wiggle “stop-in” protest was in response to their threat. Still, the police made good on their warning, issuing 204 citations over two days in August. Not to be silenced, 100 cyclists showed up at a community meeting to vent, and the crackdown was suspended.

Angry confrontations among bicyclists, motorists and pedestrians are common in many cities, but tensions in San Francisco have been heightened with the introduction of a bill that would permit bike riders to yield instead of stop at stop signs (but not at red lights, which bikers would still have to observe the same way motorists do). The proposed ordinance, backed by a majority on San Francisco’s Board of Supervisors, is expected to come up for a vote in December. If it passes, Mayor Edwin M. Lee has vowed to veto it, telling The San Francisco Chronicle, “I’m not willing to trade away safety for convenience.”

If the supervisors prevail over a veto, San Francisco will become the largest city in the United States to pass a stop-as-yield law. Idaho and a few Colorado counties are the only places in the United States that permit the rolling stop, commonly called the “Idaho stop” because of its legality there since 1982. Paris adopted a similar law this summer.