Yeah, that's going to create a sane child. One who can't be trusted to go out without a parent babysitting them every step of the way because they've been coddled so much they can't function in the real world. That's a great way to actually teach them to be an operational human being.

My 5yo knew full well at 4 not to run onto the road, and my 3yo knows as well. They wait for an adult to hold their hand, and they still look for cars as well, because they know that's what to do. They also know that if they break that rule, there will be a smack unless there was a really good reason for breaking the rule, and they even have a vague idea what those sort of reasons might be.