The legally available ones top out in my area at 20mph, or 28mph if it has a speedometer. Professional cyclists top out in that range too, and average cyclists are around 13-15mph. If you DIY with a Bafang or something, you can go 30-40mph.
I see people people running the throttle only at the limit on the ped path. That should be illegal. There should probably also be a top speed on the ped path (say, 20mph) because it’s shared by walkers, cyclists, and rollerskaters alike.








Yeah, 15kph seems unreasonably slow, and I think my kids ride about that fast. Maybe 20kph is better? I usually slow to 15-20kph anyway when there isn’t enough room to give others more than a meter of space when I pass.
So yeah, in kph, I think the regular stretches should be around 30kph, and maybe 20kph around parks and parking areas since there are likely unattended young children and pets around. I can stop very quickly at 20kph.