How about expanding the rating system a bit. Maybe a designation for a weekend only road, one for bike lanes, and one for closed to cycling. There are roads that are busy during the week, but quiet enough during the weekend to safely ride. In the USA, interstate and other controlled access highways are closed to bicycles with few exceptions. There is one exception along I-95 in South Carolina over Lake Marion to some degree, as the old bridge for US 15/301 is still standing, but closed to motorized vehicles, but left standing to allow for bicycles and hikers to cross the lake without putting them on the highway, and for use as a fishing pier.