Tim Roll-Pickering wrote:
Just noticed on Wikipedia that originally it was hoped to take the Northern
Line beyond Morden and onto what's now the Thameslink loop to run down to
Sutton - see http://en.wikipedia.org/wiki/Morden_...ailway_station

How far apart are the lines now and what would, other than line capacity,
carriage size and cost, would prevent such a connection being made today?

Beyond the physical explanations offered elsewhere, it's probably worth
pointing out that passenger numbers at these stations are amongst the
lowest in London - 23k annually at Morden South, 48k at St Helier, 86k
at Sutton Common and 99k at West Sutton. Although some of this low usage
can probably be attributed to the low frequency service (2tph per
direction), many other London stations with that level of service
achieve much better patronage.

Since there are not many other nearby competing stations, this all
implies that the stations are in pretty inconvenient locations, and a
Northern line extension probably wouldn't attract anywhere near enough
passengers to justify the cost, particularly given the lengthy journey
into London - in fact, journey times could be longer than they are now
(albeit offset by a higher service frequency).

Even the mooted Tramlink route from Wimbledon to Sutton - for which two
routes were proposed, one of which took over this railway - has been
dropped down the priority list in favour of Sutton to Tooting via St
Helier (the hospital rather than the existing station), Mitcham Junction
and Mitcham.

--
Dave Arquati
www.alwaystouchout.com - Transport projects in London