But although accidents will always happen, t0 they are much more likely to happen in an auto. The handbrake would be difficult for a tot to handle and rolling doesn't present too many dangers generally speaking. An auto will easily go 10 mph on the flat.
I don't follow your reasoning there Ben. For the vehicle to go anywhere the handbrake needs to be released. If it's on any sort of gradient it will roll even if it's not in gear. Makes no difference whether it's auto or manual. Most accidents with autos in this part of the world are caused by old fogeys confusing the brake & accelerator pedals. If they learned to drive properly using the method I previously explained this would be practially impossible.