Protesters from the Black Lives Matter movement shut down the Interstate 405, the busiest highway in the United States, late Sunday evening.

Protesters with Black Lives Matter rally in Inglewood shut down 405 Freeway https://t.co/q6BK0qD6hW pic.twitter.com/mAsVpOXwKX — Los Angeles Times (@latimes) July 11, 2016

The demonstration began after a local meeting of activists. The marchers succeeded in gaining access to the highway and staged a brief standoff with police before moving on, exulting in their display of will.

The Los Angeles Times‘ Matt Hamilton reported:

Hundreds of Black Lives Matter demonstrators poured into the streets of Inglewood late Sunday night, shutting down a major intersection and briefly blocking traffic on the 405 Freeway. Authorities said there were no arrests and no reports of violence. “There has been no reason for interference by us,” Inglewood Police Lt. Gregory Held said. “It’s all been peaceful.” Around 10:30 p.m., dozens of protesters spilled onto the lanes of the 405, forming a line that halted traffic in both directions for about 10 minutes. The crowd then moved up a La Cienega Boulevard ramp to rejoin the larger demonstration at Manchester Boulevard.

The 405 can be congested at any time of the week, day or night, for any reason, leading to frequent frustration and delays, but drivers seemed particularly irritated by a political demonstration on a night when many people were simply trying to return home and rest before the start of the work week. Cars honked as demonstrators shouted, “No justice, no peace!”

Blocking highways has been a frequent tactic of the Black Lives Matter movement since protests began in late 2014. There seems to be little point to the gesture other than as a display of numbers, and little thought for the fact that emergency vehicles might be stalled behind the hundreds or thousands of cars that must stop once demonstrators succeed in blocking traffic.

Protestors putting in that work on the 405. pic.twitter.com/rdNDCFjwhz — Jackson. (@jacksonWILL) July 11, 2016

On new innovation has been for white demonstrators to take up positions opposite police at the front of the demonstration. “Allies to the front,” one woman tweeted.

They said allies to the front line so I’m here stopping me the 405 pic.twitter.com/7hjR0gQsNs — dj hazel (@haleyymadison) July 11, 2016

Similar tactics appear to have been used over the weekend at violent protests at a highway overpass in St. Paul, Minnesota.

It is not clear what the rationale for the tactic is — whether because white people are presumed to be less likely to suffer violence at the hands of the police, or whether white protesters have to prove their mettle by volunteering for confrontation and arrest.