In fact passenger traffic has increased very substantialy.
Overcrowding is a huge problem, and I feel that it should be addressed more urgently.
SOME overcrowding is due to new, shorter trains, but an awful lot is due to growth in use.
It gets
very complicated:
At times, the new shorter trains have been for frequent, and also have made more stops to pick up drop off more passengers. Looking at one of the lines near us, from when I first used it
a) A 5 coach train every 3 hours or so
b) A 2 coach train every hour
c) A 3 coach train every hour
and so over a 6 hour period the number of carriages has risen from 10 to 12 to 18. But look at current growth rates if around 8% compound per annum, and you're heading for around 50 carriages over that six hour period - trains that are 8 carriages long rather than 3.
If you're a government (of any colour) or a train planner, though, you would have to be darned sure of your growth figures to replace the 158s on Cardiff -> Portsmouth with retired
HSTs▸ (or rather - something else that long). If growth turns out to be one or two percent under what you predicted, you'll end up with rather a lot of empty seats. On the other hand, if you underprovide and the 8% happens, people will squeeze in and you can point to the 8% to and say "but look at all this growth - of course we have problems brought on by our own success"
The "more stops" is an interesting one too. Not so long ago, Chippenham had two-hour gaps in its service during the day, but now it's a half-hourly service all day Monday to Saturday. And take a look at Bradford-on-Avon and at Avoncliff and see how the service levels have risen. The more stops you pick up at on an unbalanced run, the fewer passengers you can pick up at each stop before you get overcrowding - assuming nothing else (train length, frequency) changes.
Then you need to consider the typical journey length, and which part of the journey the train is busy on. That may be changing too. A London -> Reading passenger plus a Bath -> Bristol passenger together make use of a single seat for around 45% of the time the train is travelling. But a London -> Bath passenger plus a Reading -> Bristol passenger (same numbers on the stats!) make use of a single seat for 155% of the time the train is travelling - in other words, you have a standee from Reading to Bath.
This differential loading is interesting too. With 9 trains at current speeds, a company can run a half hourly London to Bristol Temple Meads train. And it will be much busier from London to Reading than further out from London. Or they could run a train from London every 20 minutes, but turn back alternate trains at Reading. Ergo - better capacity balancing. BUT that breaks the clockface west of Reading. It' no longer 10, 10:30, 11, 11:30 ... it's 10, 10:40, 11:20, 12, ...
There are, indeed, some trains (units) which are in place to use keep the clockface pattern, or to meet
SLC▸ specs, even where things have moved on so the SLC is now a bit silly in what it produces. An example (NOT First) of the former is a 16:51 train I caught on Wednesday. It was 6 carriages, I was on it until about 18:11 - so through an past the height of the peak - but there were never more that 6 out of 16 seats occupied in the section I was in. Of course, I don't know how crowded it would have been on its next service, at 18:26.