Basil Jet wrote on 29 September
2009 18:37:35 ...
If you download the Bank to Waterloo timetable from the TFL site, it has odd
footnotes which serve no obvious purpose.... does anyone know how this quirk
got into the system?

Thanks for the lack of a link! Select Getting Around / Timetables /
Tube and bus, scroll down to "Tube timetable - Tube line", select W&C,
select "Towards Bank", select from the list of stations "Waterloo" [1],
click on "View Waterloo Underground Station timetable" (what else do
they think I want to do?), and hey presto, a PDF timetable appears.
Well, a timetable for first and last trains and "about every X to Y
minutes" for the rest of the day. The footnotes apply to the first and
last trains, thus (for Waterloo to Bank):

a=only Wednesday and Friday, b=not on Wednesday and Friday, c=not on
Monday and Wednesday, d=only Monday and Wednesday

Then you realise that there are pairs of trains departing at the same
time, one with 'a' and the other with 'b', or with 'c' and 'd'.

My theory is that there is a half-minute difference in departure time in
the working timetable on certain days which leads to different entries,
but the times in the public timetable are rounded to whole minutes.
That theory would explain why on the Bank departures timetable, one pair
of early morning departures is listed in b-a order instead of a-b. But
I can't quite see how the theory fits the THREE departures from Bank at
21:48:

21:48 e "only Monday"
21:48 f "only Wednesday"
21:48 d "not on Monday or Wednesday"

And then of course, there's the question of why the timetable is
different at all on particular days.


[1] If you select "Bank", presumably wanting to see arrival times, you
get a PDF file consisting of one blank page, similarly for Waterloo
arrival times.
--
Richard J.
(to email me, swap 'uk' and 'yon' in address)