Large bridges and elevated roadways generally have a factor of of at least Safety 2 to 3 times their maximum expected loads. Everything these days is, for good

Large bridges and elevated roadways generally have a factor of of at least Safety 2 to 3 times their maximum expected loads. Everything these days is, for good reason, overbuilt. Even the Brooklyn bridge, partially because structural mechanics wasn't quite as well developed at the time, has a factor of safety of 6.