[angry_octet]

I think they mean that this particular element was massively overloaded (200% more than its max, which would mean 400% of the design load), not that a few cars and a truck were overloading the bridge. It was more the structure self weight that is relevant. Somehow extra load was transferred onto that element which should have been taken by other elements. It doesn't seem good that failure of one element would cause the whole thing to fall down though.