The issue with that is it's subjective.

IMO, I've found very few roads where I would ever feel safer on the sidewalk than I would the road. In the city I live in (Golden), I can't think of one road where I feel safer on the sidewalk. Quite the contrary, most sidewalks here I feel put you at more risk of a collision than the road.

Yet, when I try to encourage my friends to ride in the road, they say "It's too dangerous!" They just for whatever reason, can't imagine riding on a 35mph arterial here.