Chipping in with some hard scientific data on these two recent threads…
I just put a trip computer on the 24. First proper ride today. I make no claims to be an expert, but the figures are a guide.
After 15 minutes I’d done 1.91 miles riding fast on a level but ‘cross country’ route. Top recorded speed 13 mph.
After 30 minutes of the same sort of riding, I’d done 3.96 miles.
After 30 minutes, I slowed down a bit, did some more difficult terrain, and spent a few minutes practising idling and reversing.
After 60 minutes, I’d done 6.95 miles (having ridden for 57:44 of those 60 minutes).
Top speed overall, still 13 mph.
So that suggests a 24 (with 102 mm cranks) ridden by a reasonably experienced reasonably fit rider, and with no substantial hills, is good for between 7 mph and 8 mph if ridden with enthusiasm on mixed terrain, and ‘revs out’ around 13 mph.
(I make that an attractive candidate for the ‘If I had only one unicycle…’ debate.)
And comparing it with running? I was never a good runner, but I used to aim for sub 8 minute miles on a treadmill, and got down to 7:03 from a standing start once. That is, I could hold 8mph for a couple of miles. I could probably ‘run out’ at about 13 mph too. (All this on a machine, with no wind resistance.) So, for up to 2 miles, I’d guess the speed comparison of me running and me riding a 24 produces an uncanny similarity.
The difference is that after running 2 miles, I never had the stamina to do 5 more miles and some running on the spot! So the uni is similar in performance, but much less exhausting, so more efficient.