This was a Critical Mass event, which is why the bicyclists are taking up all of the street as a way to reclaim the streets and protest the lack of safety for riders under usual conditions. It’s not legal, but protests are never useful if they’re fully legal now, are they.
After last years was cancelled, I wasn’t sure if was happening this year. Apparently, a split in the org means there will be two this year.
I would expect Umbrella to sponsor zombie walks rather than this.