I do think it falls under a category that Americans are more and more lacking...COMMON SENSE.
You should know your kid and if he/she knows how to hang on, how old they are, their maturity level, and the proper amount of danger to put them in according to the previous conditions.
I was apparently very mature and responsible kid. Drove solo my first vehicle (64 f250) while being pulled by my dad, who was driving the JD620 pulling a drag, with the 64f250 chained behind. He said just steer it, keep the chain fairly tight and remember the brake. We went two miles and made it just fine. I was 4years old.