Puzzled about southern pacific railroad crossing in 1941 in california (possibly san fancisco)

I was watching southern pacific 1941 and ran across a railroad crossind where cars in 1941 had the right of way and the trains have so stop before proceding. I’d like to know more why that was, If being by a transfer yard has to do with it, that is a puzzle I’d like to solve. I don’t know if any else ever posted the same question if so I’d like to please see it.

thank you very much for your input