Whether it's my GT Transeo, or one of my ebikes, I average 12.7 mph, so 15 mph is a bit low. If I was careless and coasted down a hill, boom, a $100 fine for 17 mph..
I was taking a break and sitting on a bench today on the bike path when I saw a rare ebike come by. It was fat bike, in throttle mode, no pedaling. It probably wasn't doing more than 15 mph, but the knobby tires were howling, so it sounded like a crazy man was passing by.
I could accept 15 mph, but all the cardio riders would get mad.