There’s a huge international conference with a bunch of world leaders happening in SF this week, so a large chunk of downtown has a security cordon around it with police and Secret Service agents all over the place: https://sfstandard.com/2023/11/07/san-francisco-apec-securit...

(I work just down the street from this video and had to navigate the maze of fences to get to the office this morning. Aside from that the only difference from what this intersection usually looks like is fewer cars, so I’m not sure what this poster is on about.)