I believe it was at 1:40am EST. But your right that had it been during the day possibly 100's would have been killed. From every video I have seen I can't find a shot that shows a car or truck on the bri9dge at the moment it collapsed.
oh even better- there was a big rig that passed 40 sec or so in the sped up longer video- but that was it - once he passed thru the shot, not a single vehicle after.