I generally don't like riding with people. I don't mind other's drafting behind me as long as I know they're there.

I pass a lot of riders on my 14 mile morning commute. Roadies on road bikes who's hobby gets them back and forth to work. I really don't feel like slowing down and chatting, but I'm more than happy to let them draft across the often windy Yolo causeway if they so desire.

How do I let another rider know it's OK to draft as I pass them?