In message , at 12:53:11 on
Wed, 20 Jul 2011, Jeremy Double remarked:

Many people would kill for 4tph. My own view (coloured in some part by
being a past user of the outer fringes of the Met line) is that
something magic happens between 3tph and 4tph - despite it only reducing
the interval by 5 minutes. Such that 4tph is a frequent enough service
it's turn-up-and-go for most users.

Only if the 4 trains per hour are evenly spaced...

Agreed. I've often said how East Midlands Parkway's 2tph is really two
trains once an hour.

The core Shipley to Leeds service has 4 trains per hour. But the
trains have departure trains of xx:09, xx:14, xx:39, xx:44. This isn't
really turn-up-and-go.

The airport services at both Amsterdam and Geneva are numerous, but
quite poorly spaced, which catches some people out.
--
Roland Perry