Overpass API query: How to return outermost nodes only?

I'm working on a bit of an isoline/catchment issue for some set locations.

I need to get an idea of where the road extents are within a given radius or bounding box

eg: 5km, 10km, 50km of the facility.

I can do this with queries like the one below But I don't need all 70,000 points (5mb), I just need to know the outer reachable ring. This is more of an issue on the coast where I basically need to know the closest road to the beach.

http://overpass-turbo.eu/s/sRf

[bbox:-37.964903,144.682029,-37.764903,144.882029]; way[highway~"^(unclassified|residential|living_street|service|motorway|trunk|primary|secondary|tertiary|(motorway|trunk|primary|secondary)_link)$"]->.road1; node(w.road1); out;

Any suggestions?