I think your focus on peak load is misplaced, and misses an important part of the value offered by rail, especially as routine commuting has declined.
It's a mentality that presumes that capacity that is not fully utilised at all times is wasted, but doesn't acknowledge that some "spare" capacity is necessary to make things work (see also hospitals and bed utilisation). My observations of ECML trains is that loadings are high, but not necessarily in the traditional peak.
I'd also suggest that if there is residual capacity available, it leaves room for more economic growth at lower cost - if trains were already fully laden at peak, you would either have to consider pricing off demand, or make some very expensive purchases.
I am sorry, but I don’t agree with any of those arguments.
Effective use of peak capacity is critically important in the intercity routes for a whole host of reasons. We should not have trains running around half empty in the peaks for want of thinking again on ticketing strategy.
The comparison with hospitals doesn’t work. Once the seat has not been used, it will never be used for that journey. The capacity has been wasted even though the costs of providing it have been paid.
In a hospital, you ideally need an element of spare capacity to deal with a surge. It is a very different situation.
A train with 611 seats can take 611 customers sat in those seats perfectly well day in day out.
The residual capacity argument doesn’t work, because our economy is not growing. Therefore we need to create economic activity now, utilising assets and capacity that we have already paid for first. We do not have the luxury of being able to waste that capacity.
The idea that you somehow pay the very expensive infrastructure costs for capacity to be available, pay for the running costs to keep it available, but then actively accept not utilising it does not work.
If trains are regularly less than 50% loaded, they should probably cut the number of services in half. If they did that, they would have to say ‘we couldn’t work out a way to fill the peak trains’. The country would scream back ‘it is the fares - we want to use them’.