[potatoz2]

Are they very dangerous for children? Are there statistics?

It doesn’t really freeze in Paris anymore so it's a moot point, but you can ride bikes when it does (you need different tires, just like cars, and a city that clears the roads, just like for cars).

[Saline9515]

A bike going at full speed on the sidewalk is dangerous to children, yes. It is why many cities banned cyclists there, which as a result led to a decrease in accidents. Pedestrians don't go at the same pace and can be particularly vulnerable, so I don't see why you need a statistic to understand this basic fact.