Peter Masson wrote:
"zin92" wrote in message
oups.com...
Apologies in advance if the below has been considered before (I did do
a search).

Obviously the current proposal at London Bridge is to build a new
viaduct west of London Bridge station carrying two more tracks. This
will allow more trains between a) London Bridge and Charing Cross and
b) London Bridge and Blackfriars. However this will have a significant
detrimental impact on Borough Market, is very costly and is likely to
take many years to implement (even once approval has been given).

However it occurs to me that there are alternative solutions that can
be built quickly at relatively low cost with no impact on Borough
Market. They probably won't allow quite so more trains per hour but
they will allow the number of trains per hour to be significantly
increased. I'm not sure whether they are an alternative to the current
proposal or a short-term fix ahead of the proposal.

One of the main problems at London Bridge currently as I see it relates
to platform 5. The track alongside it is reversible which in theory
makes a lot of sense: in the morning peak, (busy) westbound trains can
use both platforms 5 and 6 whilst (less busy) eastbound trains use
platform 4; in the evening peak, (busy) eastbound trains can use both
platforms 4 and 5 leaving platform 6 and the platform 6 loop line
(which has no platform) for (less busy) westbound trains. However in
practice, the use of platform 5 by westbound trains causes problems as
they can only regain the route to Charing Cross or Blackfriars by
blocking access to platform 4 to eastbound trains (whilst they traverse
track shared by platforms 4 and 5).

I suggest that a new platform should be built alongside the platform 6
loop line. Let's call it platform 7 - not to be confused with a
previous platform 7 which is no longer in use. This would allow
westbound trains to use platforms 6 and 7 at all times whilst eastbound
trains can use platforms 4 and 5 at all times. This would allow
significantly more westbound and eastbound trains per hour as westbound
trains would never block eastbound trains.

There are a couple of (small?) disadvantages to this. Building a
platform 7 would mean that platform 8 would have to be closed as
platform 7 would block the track leading to platform 8. Platform 8 is a
terminus platform and I don't think it's used very much (and so
hopefully closing it would not cause a problem). The other disadvantage
is that passengers waiting for a train to Charing Cross or Blackfriars
would need to use either platform 6 or platform 7. Unfortunately there
would only be footbridge access between the two (as oppose to just
walking to the other side of a shared platform). And similarly for
eastbound passengers who would need to use platform 4 or platform 5.

As far as I can see, the above can be achieved quickly and a low cost:
a new platform and minor trackwork alterations only.

I think that the second main problem at London Bridge currently is that
westbound Thameslink trains cross over the path of eastbound trains
from Charing Cross on the level. I wonder if a solution would be a
flyover just west of the current viaduct. The flyover would connect the
westbound track over the viaduct with the westbound track to
Blackfriars.

I think that the flyover could be built over the middle two tracks in
the four-track section west of the viaduct. Obviously this would mean
that four tracks would be reduced to two for the distance of the
flyover. However I don't think this would be a problem in practice as
four tracks reduces to two over the viaduct in any case.

Obviously building the above flyover isn't cheap. However, surely it
would be significantly cheaper than building a new viaduct parallel to
the current (and no impact on Borough Market).

Just a thought. I'm sure there are reasons I haven't thought of that
make the above two proposals impractical.

The double track section between London Bridge and Metropolitan Junction is
already the busiest double track section of railway on National Rail, with
up to 30 tph each way in the peak.Additional platform capacity at London
Bridge, or the flyover suggested, won't relieve this congestion., so these
wouldn't enable any more TL trains to be run via London Bridge. The
additional platform would allow trains which now use the Up Passenger Loop
to call at London Bridge, but I cannot see that there would be any other
advantages. Although I haven't seen a recent WTT, and avoid London Bridge in
the peaks, AIUI use of platform 5 by up trains in the peak is minimal,
mainly because they block down trains on the Charing Cross side of London
Bridge. In the absence of stabling sidings at Charing Cross, or the former
sidings at Southwark (Ewer Street), everything that runs into Charing Cross
has to run straight out again.

I hope TL2xxx will soon be approved, and funded, as it is the only hope for
relief of congestion on the Charing Cross, Cannon Street, and Thameslink
lines.


One frequent cause of delays is not so much the busyness of the
two-track section, but the fact that trains heading for platform B at
Waterloo East, and occasional Thameslink trains, get trapped in the
bottleneck by trains coming from Platform C at Waterloo East.

The fact that this happens so often means that the section can't really
be at capacity in terms of moving trains that could fit through, but
any solution I can think of, like pairing by direction through Waterloo
East, would cause horrible crossing movements between there and Charing
Cross instead. Maybe any flyover should be near Jubilee Gardens
instead?

I agree that the extra through platform at London Bridge wouldn't help
much. I suppose it would allow people who wanted to get off at London
Bridge a chance to get into the platform, but once there was one extra
train in the station, there would still be nowhere to go.