Last summer there were a couple of cross country skiers on the trail, training on rollerskis with ski poles. I only caught up to them on hills and had to wait for a long hill before I was able to pass them. These dudes were quick on the flat and scary fast on the downhill sections.
Also had some kid blow past me on a onewheel electric roller board (single fat roller in the middle - sort of looks like a balance board) Kid must have been doing well over 20 mph in shorts, tee shirt, no pads, no helmet. Oh to be young and indestructible again!