If you're having trouble visualizing what happened (like me), here's the intersection: https://www.google.com/maps/@37.3859058,-122.0843836,3a,75y,180.9h,70.85t

If you're having trouble visualizing what happened (like me), here's the intersection: https://www.google.com/maps/@37.3859058,-122.0843836,3a,75y,180.9h,70.85t/data=!3m6!1e1!3m4!1sT2jrKcM8pLU8MPq1hj60xQ!2e0!7i13312!8i6656!5m1!1e4!6m1!1e1 https://www.google.com/maps/@37.3859058,-122.0843836,3a,75y,... Looks like the far right lane has double the normal lane width to accommodate on-street parking. The Google car, looking to turn right on red, attempted to use the right-most part of the lane to pass cars that were waiting to go straight, but there were sandbags covering the storm drain near the corner, so it had to stop. When the light changed, the cars it had passed continued on while the Google car waited for a gap, which ended up being in front of a bus, likely caused by the bus accelerating more slowly than the cars in front of it. The Google car tried to use the gap to get around the sandbags, assuming that the bus wouldn't just plow into it, but the bus plowed into it. Perhaps the bus driver assumed the Google car was parked and wasn't paying much attention to it.