That hip bar isn't holding your child in.
In a turn, a small body swings over the side bar. The bar becomes the pivot, and the head, the heaviest part of a toddler, goes over first. Pediatric trauma records show it happening at speeds as low as 11 mph. That is slower than most neighborhood loops.
Mechanism described in peer-reviewed golf-cart injury studies (National Library of Medicine / PMC) and pediatric trauma-center data. Full citations available on request.