On 13 July, 11:55, John B wrote:
Presumably the logic is that if we're extending the GOBLIN platforms
it might as well be to 4 cars (which'd be either 2x172 or 1x378
depending on electrification status), hence ordering and carrying out
work for 3-car 172s would be completely pointless.

No, three car 172s are definitely the plan, but the idea is that the
other committed capacity increases will delay the necessity of three
car trains for some time.

Peak capacity goes up by 33% when they introduce the 4 tph timetable
at the end of this year, and a further "30%"* when they introduce the
two car 172s some time in 2010, then at some later date three car 172s
will be introduced.

(Using these numbers, four car 172s every 15 minutes would have 3.5
times the capacity of the current service, which is simply not
justified by current or any foreseeable near-future demand)

U

(* this is TfL's number for 150 vs 172 capacity)