I assume you are too young to drive a car, or don’t have a license.
These are both dreamsigns: if you notice them, then you become lucid. Also, you can’t do them in real life.
I think that formula for effectiveness is not very useful. It’s more important to know how often you actually get lucid from it.
Dreamsign “Accuracy”: Recognised / Total
Dreamsign “Frequency”: Nights Seen / Total Nights
Dreamsign “Usefulness”: Accuracy * Frequency
These terms I have just invented myself. Is good?
The UFO is therefore the more useful dreamsign, and the other one is not useful at all. I suggest you try to make it useful.
Look into that newish method, um… that MILD variation… Trancewave? Here you go.