Nice wide CLEAN shoulders WITHOUT rumble strips/stripes can make for a safe road, but those are usually limited to high speed, high traffic main artery roads. Those roads are generally rideable and good when you need to get from point A to point B, but difficult to turn left from, risky in terms of right hooks, and generally not very much fun.

When I look for roads I prefer to ride, traffic volume is the #1 consideration. Sight lines and the like are largely dictated by your terrain. Traffic volume tells me how much in a hurry the drivers will tend to be, how many cars I might hold up while climbing a hill, crossing a bridge or approaching a blind curve, and just generally how often I will have to interact with traffic.

Have a mirror and learn to use it. Understand when and why to take the lane.

How often I have to drive somewhere - well right now, because of my injury, always - but in terms of roads, never - although I wasn't riding when we bought our house, traffic volume was definitely a consideration when we bought it. But since I prefer to ride with people and live far from the county seats, when I was healthy I would often drive to the start of a group ride. It really depends on where you live. There are some roads I would never ride on, and if I lived on one of them, I wouldn't ride from home.