My biggest fear is the person who is driving a Chevy Subdivision while eating an Egg McMuffin, drinking a cup of coffee and talking on a cell phone jammed under their ear. The road is the last thing that gets their attention. A bicyclist is just a bump in the road.
I stopped riding on the street when a friend's Dad was killed in an accident with a motorcycle at the end of a 35 mile bike ride one mile from home.
Of course on the trail you have to contend with people walking 4 abreast and failing to yield the trail. At least the grass is softer.