Single Yellows mean that there is “danger” up ahead.. and no overtaking, etc.
Double Yellows mean there is “serious danger” up ahead.. and prepare to stop.
Only problem is that the definition of “danger” is fairly fluid. A Single Yellow could mean a car is parked off the racing line, or that someone has buried it in the tyre wall on the other side of the track.
When Racing, no-one wants to give away any time at all, and drivers will try and make it through the Yellows with little to no time loss.. For example, when Karting they throw the Yellow even if there’s only a kart off the racing line in the Gravel. It’s gotten to the point where no-one actually slows down for the Yellow, and everyone keeps the throttle pinned hoping that the crash is out of the way..
The Marshall’s need to decide on a definite Yellow meaning, and they need to enforce the “no passing rule”.. The “Double Waved Yellows” idea is good, but they need to only use it on extreme occasions to avoid the “boy who cried wolf” kind of result