The news said they were a 67 & 64 yo couple from Garden City UT (Bear Lake). It didn't mention the bump but did say they started to sway and lost control. The semi driver that nosed in and chained to them deserves a free dinner.
It is possible that a wind gust up the canyon caught them. The bridge has high sides to help that but it's not a cure all. I'll still bet on the bump.
I couldn't tell from any of the pics if he had an equalizer hitch or sway bars. That might have saved him.
