judging by one of the vids I've seen there were cop cars etc on the bridge when it fell
The video clip I just saw showed some truckers taking a big chance but making it across from right to left (with the boat on the far side of the bridge). Didn't notice any flashing police lights either end. Maybe cops were in place on one side of the bridge stopping traffic but not on the other side. ????
Bridge came down within seconds of the impact.