Adrian Auer-Hudson wrote:
What would it take to make at least one of these, GC and Piccadilly
Line, pairs into an interchange station?

It would be far too expensive to be worthwhile, when interchange between
Chiltern and Central lines at West Ruislip provides access to the same
general corridor.

Marketing and information provision would probably improve the current
situation cost-effectively. The two stations (Sudbury Hill, Piccadilly
and Sudbury Hill Harrow, Chiltern) are as close as the Central and
Piccadilly platforms will be at Park Royal (i.e. not ideal but not worth
moving one of the stations).

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London