I draft behind trucks. Small trucks with trailers, or delivery trucks are the best. I look for a line of 3+ cars - because if I draft off on one car, they will always speed up - but if it is 2+ cars the car in the front doesn't know I am back there. Still, drafting on gravel sounds like a good way to fill my lungs with dirt. ;-)
Here is yesterday's draft. Speed limit is about 25mph along a twisty lake shore, so I usually can pick up the tail in of a chain of cars if I'm lucky. Not bad for a gravel bike. ;-)
