On Apr 12, 6:17*pm, "Paul Scott"
wrote:
Andy wrote:
DfT have indicated that they are willing to accept less than 140
vehicles, if it involves use of existing stock. The planned 458/460
rebuild would provide 54 extra vehicles and the 456s an extra 48 to
give a total of 102. Making up the shortfall of 38 (about 27% of the
planned vehicles) would have to depend on new build. (This was all
covered in the February Modern Railways).

Yes I saw that - I folowed the text OK, though I thought Roger's latest
table was a little confusing, because he included the existing 458s - which
on the face of it *shouldn't be there as they are already in current use -
but not the 456s.

With regards to running the trains at maximum length, in peak
direction, it would be easy to diagram the 10 car trains to be
arriving in Waterloo in the 08.00-08.59 'main' hour, with the 8 cars
running the other services and / or those on the less busy branches.

But the same NR table explains that by running ALL suburban trains at
maximum length (which apparently requires only 12 extra vehicles) 1,200
extra seats become available across the whole three hour peak.

However what is more relevant in context is that this provides no increase
at all between 0800 and 0859. *That suggests all suburban trains that could
run as 8 car between 8 and 9 already do. *A subsequent look at the Waterloo
CWNs also supports this view. *(I also recall there are no single 455
diagrams at all on weekdays.)

Therefore as there are supposedly no additional paths available, nearly all
the suburban increases must be due to train lengthening, indeed the
figures are vastly different - 1,200 by running all trains at the current
maximum, but 19,200 by running all at 10 car.


But there is no mention as to the effect of diagramming the 10 car
class 455/6 trains into Waterloo between 0800 and 0859 whilst
retaining the 8 car trains on the diagrams which arrive earlier or
later. Depending on demand, it may not be necessary to run all trains
at 10 car length. With minimum round trip times (between a train
leaving Waterloo and arriving back) of at least 1h 20 mins, having
half the services as 10 car and half as 8 car will allow more than
just the 0800-0859 arrivals to be lengthened.

I would say it is impossible/very expensive to convert the whole 455
fleet to 10 car operation (along with consistent power per unit when
running in shorter formations). Of course, in the future, 12 car will
be easy.

Which is about where we started - only able to lengthen half of the 455
operated services.


Unless there is a cascade of 455s to/from Southern in order to match
455 and 456 fleet sizes or to allow some 455s to be shortened until
such time as 12 car trains are needed. Another possibility would be to
bring forward the lengthening of the 'busy' SWT routes (for example
the Woking slows where the country end stations are already long
enough) to 12 car and just run the other routes as 10 car.