How many 319's are going to Northern and when will they start arriving up here?
The first part of that is an unknown. Northern will initially receive some 4 car 319s.
However, Thames Valley may or may not receive 319s. The original plan was for those routes to have 319s until CP7 when likely new 5 car 110/125mph units would be ordered. However, some people are suggesting with the Thameslink delays Thames Valley might go straight for the new trains.
It is also unknown whether all 319s will remain in 4 car formation. The Bolton corridor in particular already sees some busy 4 car local services at peak times, so keeping them 4 car and using them on the Bolton corridor means either the cascaded trains will be overcrowded with very little growth or a platform extension program will have to be undertaken (which isn't included in Network Rail's CP5 plans.) Porterbrook have unveiled an option to reform 319s in to 3 car trains with corridor connectors, which would then work on the Bolton corridor. However, that obviously means some carriages go to waste and the 319 fleet don't stretch as far.
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The NW wires will require 13 units in Dec 14 and 24 units for Dec 15. Total of 37 units.
6x 319 will be freed in May 14 and with all the 387 fleet releasing another 29x 319 by May 15. A total of 35 units by mid 2015.
Out of interest does that calculation allow for Liverpool-Victoria stoppers going half-hourly all day and also Stalybridge-Manchester being done as an extension of Chat Moss electrification opposed to stage 1 of North TPE electrification?