Stoke to Manchester - the pre-Covid timetable had 4 fast services and a stopper each hour.
A brilliant level of service, you might think. Not quite - the departure times were xx05, xx15, xx27 and xx35 off Piccadilly for the fasts, followed by the stopper at xx47. So a half-hour gap in fast services if you were unlucky enough to miss the xx35 (albeit the stopper is 'only' about 15 mins slower than the fast, so is still just about worthwhile taking).
It's similar, if slightly worse in the northbound direction, with fasts at xx20, xx25, xx44 and xx48 followed by the stopper at xx56. So again an effective half-hour wait if you miss the xx48.
As part of Covid timetable reductions, you might have thought that Avanti and XC (the operators of the fast services) would collaborate to ensure that there was still a reasonable service. But no, even today the pattern in most hours is that just the xx44, xx48 (and xx56 stopper) run. Meaning the service is only slightly better than hourly.
Now Stoke to Manchester isn't a huge market, and there are reasons why certain services were removed but not others, but it's just an example of how having lots of trains per hour is useless if they aren't spaced appropriately apart. I'm glad I don't live in Stoke (though that's perhaps not the only reason why!
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