Honestly, my thoughts on this is there is no need. I worked in daycare for years. I had many kinds of children in my care. I took every single one of them on a walk while holding onto a walking rope. (Think of a rope with little loops they can hold on to). It is like a child holding your hand, but 20 of them. We walked on busy streets and there were no issues. We talked about what was required and if they did not listen they could not go next time and followed through with it.
With my own son I would hold his hand and walk with him. When I was getting things out of the car he had to touch the car with one finger so that he wouldn't get away from the car and get hurt. Literally touches the car with one finger and I know I can trust him not to bolt. He knows that means he goes back into the car and it is over.
I guess I just do not see the need. Someone enlighten me please.