Thanks both of you, useful background. What I really need to know on top of this is what actual service is typically offered to transiting traffic on route 1 and 4. I think I can probably infer that it's visual from the subsequent comms. That is the core difference between the London Heliroutes and those in DCA. In London it's Radar service only for helicopters on the routes, with the possible exception of the Battersea LFA. Hard to see why that wouldn't be the same for DCA.