that is not of 1906, its of 1905 as someone pointed out.
this is the original place the video was posted
FORA.tv - Rick Prelinger: Lost Landscapes of San Francisco
click on "Chapter 12- A trip down Market Street Redux"
The video was staged, on a ride down Market street. The cameraman paid his friends to zig zag in n out of traffic to give the film "a little more visual interest"
There are many more videos on that link too btw. Enjoy.