Most MUP's I've been on at some point list the top speed at 15 mph at most. Not that I've ever seen a cop with a radar gun out there, but I don't tend to go too fast on them unless it's a really out of the way area with long sight lines and no one around (except maybe a couple of other fast moving commuters).
I have both a bell and an air zound to let people know I'm there, but the air zound is mainly to interact with cars and I can't say I've ever used it on the MUP.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"