Mike, thanks. That is interesting stuff about ADS-B.

It is, of course, up to you guys in the USA to choose whatever is best
in the meantime. I still think that a wise choice should depend upon
the risk data, and I don’t see anybody answering the question about
the USA data for glider collisions, how many and what sort of place.

Until we looked at the UK accident reports over a long period, some
people had thought that cloud street running was likely to feature
prominently in our collisions. Turned out not so – not a single such
collision. As I wrote above, most are over or near the home site of
the gliding operators (glider, tug, motor glider). Some were in the
circuit (pattern, I believe, in US terminology), some thermalling. A
very small number were elsewhere, thermalling.

Chris N.