It also stopped in a bad spot for human eyes. From the rear facing shot, looks like was just past a brightly lit to dark tunnel. Human eyes need a bit to adjust

It also stopped in a bad spot for human eyes. From the rear facing shot, looks like was just past a brightly lit to dark tunnel. Human eyes need a bit to adjust to that. It's quite possible, especially as the backup grew that people literally couldn't see the brake lights. Thats not to excuse anyone, but it may have been a contributing factor.