On this Youtube video at 7:17 there is a brief scene showing traffic moving in one direction along Sepulveda Blvd through the pass.
https://www.youtube.com/watch?v=8RSy1QkAPSc&t=731s
I know I have seen similar footage elsewhere. Was this a reality? I.e. did the city highway department basically direct all cars in one way along the stretch in the 1960s prior to the construction of the 405 freeway to help with rush hour traffic or was this just a "made in Hollywood" type of fiction?
It looks like the cars, other than the one carrying the camera, aren't moving at all. My guess is that this was clipped from some movie or TV show.