I always try to wave at approaching Airstreams (Though I admit I don't always recognize Interstates from otter Sprinter class B's) having been used to doing so with Brit sports cars I have owned and also on motorcycles.
With motorcycles, it is surprising to find what a friendly and helpful bunch they are whenever you meet upon the open road. Well mostly anyway, haven't had any bad experiences with "One per centers" yet!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.