hadw
12
Whole country queries are always going to be slow.
I think you are still relying on the none speed limit actually having been set everywhere that it applies. My guess is that, if it has, it will have been imported from elsewhere, and you would be better off starting from the upstream source, as it may well be authoritative.
Also note that your query will almost certainly return two results for every stretch of autobahn, and may return more.