I just spend a week biking in MN, Root River Trail system. We stayed in Lanesboro. Sort of the center of the trails. My routine was to do 50 miles Lanesboro to Harmony and back in the AM on a Madone. In the PM do 60 miles Lanesboro to Houston and back on a Tandem. The trail has grades to 10%. That is why that trail is sparsely used. On a given morning I have seen 4 bikers.
Now the safety issue:
I go as fast as I can up the hill but limit my speed to not much over 20 MPH down the hill. There are a lot of little critters, an occasional jogger, some sandy patches, some wet patches. On one day there was a mother being pulled by her dog to one side and by her child to the other side effectively straddling the trail. I was able to stop safely and waited for her to get things under control.
That same day, there was a biker ahead of me, male and under 30, going down the long curvy hill as fast as possible (for him). I met him a little later. He was standing at the side of the trail all bloodied up. Hands, knees, legs. It is amazing what asphalt will do to you at a high speed fall.
I also shudder at the thought that he would have run into the above mentioned mother, child and dog.
That MUP is not good for maximum speed biking.