Becky Guy said her daughter and her dog are often in the garden
If the choice is between endlessly letting reckless drivers crash into your hedge and hoping that they don't injure anyone else while waiting for the council to do its damn job and put a speed restriction up and running the risk of said reckless drivers sustaining more serious injuries then I think that in that imperfect world I might invoke caveat rector.
Why did you start this post with the American phrase "Rookie mistake"? You probably thought that it pithily encapsulated something to do with your point. Or maybe you're just a... what is it you young people say? A "memelord"?