On Sat, 09 Dec 2006 13:13:33 +0000, asdf
wrote:

On Sat, 09 Dec 2006 12:56:30 +0000, Paul Corfield wrote:

But why don't they do some similar bribery to get more trains running on
the overground ? I come in from Palmers Green to Moorgate every morning
and there are huge gaps in the service.

I think the issue will lie somewhere between DfT and Network Rail. DfT
is more interested in screwing huge premiums out of franchise holders
than it is in getting more trains running or funding an expansion in
infrastructure. The lines out of Kings Cross and Moorgate are pretty
much full in the peaks due to the need to mesh fast, semi fast and local
trains on the tracks alongside GNER, Hull Trains and soon Grand Central.

But those trains don't use the Hertford Loop (the line through Palmers
Green). The section from Alexandra Palace to Finsbury Park might be a
bottleneck, but aren't there extra tracks there?

Yes and where do they then go? Moorgate is a very tight bottleneck and
Kings Cross is pretty much at capacity AIUI. Mr Cowling is complaining
about the peak timetable IIRC.

I was thinking Moorgate. It currently handles 12tph in the peaks;
Brixton has the same layout and manages 30tph. But I suppose it's not
that simple.

Platforms are shorter and narrower and much more congested at Moorgate
which may create some capacity and safety issues - I am speculating
though. There is also the issue that the flows are heavily peaked - I
can't see there being demand for a high frequency n/b service from
Moorgate in the AM Peak. There is much more two way demand at Brixton
given the tube is a gateway onto a huge local bus network into South
London.

Crews would need to "step back" to increase turn round to LU standards
thus adding to costs. I think the track approaches at Moorgate are far,
far tighter and are speed controlled thus lowering capacity. Given the
history at that location you would need a lot of work to raise approach
speeds and junction capacity without increasing the overrun and
collision risk.

Brixton is a much faster approach, there is auto train control and long
overrun tunnels so is safer. I'm not sure about relative acceleration
rates on the stock but the tube *might* be a bit faster. Obviously this
will increase considerably with the new V stock in a few years time thus
improving the capacity yet further.
--
Paul C


Admits to working for London Underground!