I ride the local MUPs once in a while. There is one in particular which connects towns, which from my door to the end and back is 52 miles, a nice ride. It stinks riding it until you get about 3 miles south of town. You have to attempt to get people to move aside who are walking (if the pace of a zombie is walking) 5 abreast. You have to skirt dogs, children (usually worse than navigating dogs) and people who cannot ride a straight line on a bicycle. After that it is great, maybe 5 riders per mile who are pretty curteous.
For the most part I am good with highways and streets. I may be slightly safer on the MUP, I certainly have much less stress on the road.