What is the proper etiquette to let a person know that they have a crock pot on the roof of their mini-van?  I don’t know morse code, I don’t know that it is safe to exit my vehicle while driving with two little girls in the car to alert the driver of the crock-pot-mini-van, and I’m pretty sure that when traffic is that jammed and it is as cold as it was this morning (-13F or -25C) its even less safe.  What would you do, if anything, to alert the driver that their soup is getting cold?