His peak figures are for half an hour. The Northern line figures he
quotes
are therefore as follows, in trains per hour:
Peak Off-peak
Northern (CX) 20 15
Northern (Bank) 20 15
Northern (South) 30 20
(Thanks, Peter, by the way. Very useful.)
--
Richard J.
(to e-mail me, swap uk and yon in address)
Ah, that makes more sense - I didn't pay much attention to the actual time
span being ½ hour.