On Sat, 29 Dec 2007 18:00:13 +0000, Tom Anderson wrote:

The clever bit about the Bakerloo tunnel is that it allows trains that
would otherwise have to reverse at Queen's Park to go somewhere; if the
plan to reorganise the DC lines comes to pass, so that all Bakerloo
trains can go beyond Queen's Park, with NR trains (from the Overground)
terminating there, this becomes a less good plan.

Possibly-ignorant question: why can't some Bakerloo trains go beyond
Queen's Park? I looked on the interweb but couldn't find anything about
some trains being different to others.

Sorry, i phrased that badly. All Bakerloo trains are, as far as i'm aware,
capable of going beyond Queen's Park - it's just that some don't currently
have the opportunity to do it, because north of there, the track is also
used by suburban trains from Euston (QP being where the Bakerloo tunnels
and Euston surface tracks join up), so there isn't enough capacity (AIUI).

There's only 3tph from Euston north of Queens Park, but many more
Bakerloo trains than that terminate at QP.

I think the main reason is simply that the outer part of the line
doesn't require as high-frequency a service as the central part.

It's interesting that the arrangement here is the reverse of the
normal situation - instead of one central route with two outer
branches, there are two routes from the centre combining to form one
outer branch. I'd say the clever bit about the Bakerloo tunnel is that
it would re-balance the situation (especially with the District
currently having too many western branches).