You guys are on it. COLREGS should always be the first place to look regarding ROW questions.

Fire helicopter vs. sailboat? Thankfully, you don't see THAT every day! (Yes, we call them wildfires, also known as forest fires or brush fires as appropriate.)

Now, whether or not you believe that the US interstate system was designed for this; occasionally, small planes do make emergency landings on highways. Where does it say who has the right of way there?

Mike