Roland Perry wrote:
In message
-septe
mber.org, at 10:06:07 on Thu, 24 Nov 2016, Recliner
remarked:

Incidentally, although the Piccadilly line is largely above ground from
Baron's Court, it's largely on viaducts rather than cuttings, so it
shouldn't be affected very much by leaf fall.

And the branch to Uxbridge, and the part in North London?

Very little of the eastern end is not underground.

The Acton Town to Rayner's Lane section is on viaducts from Park Royal most
of the way to Sudbury Town, where it's at ground level. It's then in a
shallow cutting till after Sudbury Hill, after which it's back on viaducts
to Rayner's Lane. It's then a mixture, but I can't think of any deep
cuttings on the rest of the route to Uxbridge. Remember that all of these
lines were built by the Met and District lines, rather than Tube railway
companies, and they preferred to build on or above ground level in the then
largely rural areas.