My 3 year old never ran into the road, and as a six year old she would keep a tight leash on her little brother if he ever tried to do that. I’d for sure let them walk down a residential street by themselves.
Sure, in a calm environment. But when kids start having fun together - they lose control of the boundaries and can inadvertently run on the road without even noticing it.
You just described nearly everyone I went to university with.