How do you determine which roads are safe to ride on and which should be avoided? What traffic patterns do you feel comfortable riding in, and which ones set off alarms? What sorts of intersections do you avoid? How about for nighttime riding; are the same roads safe at night, or do you take a different route at night than you would during the day? Are there any statistics on ratio of accidents to total bicycle usage on certain roads to help inform this decision?
There are several streets in my area that I will always avoid. There are a few parkways with no shoulders whatsoever, narrow lanes, winding roads, fast moving traffic, and very few stop lights and side streets to calm traffic. There are several that I feel pretty confident on, with reasonably wide bike lanes, low traffic, and frequent intersections that mean that traffic doesn't usually get too fast and drivers are on the lookout for people turning in. I'm just wondering if there are any more objective criteria I can use, or good rules of thumb, for where it's safe to ride.