Considerate driver of the day

It used to be a circular motion with the hand to indicate slowing down but no one really knows that any more and it would just be confusing. Wrongcog has it spot on I think.

This is true although it's an up and down motion, circular is to turn left (highway code) it is still on the driving theory test and is the same signal for cyclists, and no-one has any idea what it means. I'd just stick with eye contact and anything that seems to resemble stopping.