>one should always be careful to not drive off a cliff, or off the outside of an unexpected turn in the road, or into a fallen tree, or into a pedestrian, or into a stopped car

All of those examples are more visible in low-vis conditions than a missing bridge, due to the presence of physical objects - e.g. cliffs and unexpected turns always have barriers/signage. A missing bridge is the absence of an object. I think this is a really particularly easy case in which to give the driver the benefit of the doubt.