But it was a big part of rail revenues which may now travel off-peak and also encompassed anytime business travellers, demand for which has dropped off a cliff.
So in some ways it is a challenge at the very least.
The issue with a very high peak flow is that there's the potential that some units run just 2 services a day (one inbound and one back again).
Assuming lease costs of £200,000 per coach and a 4 coach unit and lease costs being 1/3 of all TOC costs, that's £2.4 million a year.
Assuming 70 seats per coach plus 30 people standing, that train basically needs to be rammed with people paying £6,000 a year in season tickets.
Conversely, if it's only doing off peak travel and runs 4 return trips a day (we'll assume 330 days a year to allow for maintenance) running at 29% of seating capacity (80 seats per unit). The ticket price per person would need to average £23 return.
In a real world example Woking to Southampton evening out return* is £27 and the season ticket is £6,528 (so close numbers so we can reasonably scale them.
If we scale the season ticket down that would be £5,560, which is lower than the required £6,000. On that basis the off peak trains would break even whilst the rammed peak trains would make a loss.
In reality there would be a mix of tickets being used across trains across the day.
However, the reality is that there were likely fleets in the southeast where, if there wasn't the need to cater for the very high peak flow that the number of units could have been reduced.
Typical peak travel is 1 in 10 people traveling between 8am and 9am, yet there's typically 13 hours of train services (excluding the reduced frequency often seen after around 9pm). For rail that's more typically 15% and sometimes rising to 20%.
If we have a baseline of 1,000 heading towards "City A" that's 150 in the morning peak and an average of 71 each of the remaining hours.
If Covid means that 150 has reduced by 20%, so that the morning peak is now 12% of daily flows, if the total passenger count is still 1,000 the numbers alter to the following.
Morning peak hour is 120 and the off peak average is now 74.
The issue the railway's really have is the distances traveled, whilst peak hour travellers may well travel for 30 minutes, off peak they are likely to travel shorter distances.
This means that to earn £100, the railway's need to have more people traveling off peak than peak. However, as these are shorter trips it could be that the peak capacity needed isn't any higher (for example on a train between Southampton and Woking a seat maybe used from Southampton to Eastleigh, Winchester to Basingstoke and Fleet to Woking and generate a similar income as one person traveling Southampton to Woking (yes there's gaps, but due to higher costs per mile for short station hops this can result in a similar total).
The complexity is that WFH can mean that peak hour travel may have only fallen 10% on the busiest days but 20% on the quietest.
I do wonder if the railway's are missing a trick in that they could offer a flexible season ticket. What it could offer is a monthly ticket based on allowing unlimited peak travel, but with a tap in uplift to "upgrade" a given day to permit peak hour travel.
In doing so it could allow people to use it for other travel (visiting friends, going shopping, going to work off peak for a meeting on a day they don't normally go to the office but the meeting time means they don't have to use peak time trains, etc.).
Pricing might be tricky to pitch, but based on Southampton to Woking if it were 16 days at £27 (£432 for the month) with a £6.50 daily upgrade for peak travel (compared to the £7.50 price difference). For anyone traveling less than 175 days of peak travel that's cheaper than the annual season ticket.
For within the month, chances are it'll only be worth doing if you make some extra trips (even if they are one station hops) and are working in the office 3 days a week (and even then the advantage of just paying a monthly amount, plus a tap in charge which is taken automatically for the "anytime" days, and not having to buy tickets each day could be of value to some).
The point being, that if they then wanted to go somewhere else (London, Reading, Guildford, etc) they'll almost certainly pay the extra to extend their ticket rather than drive. Overall, whilst some may get it to work in their favour, it's likely to act as a boost to the railway's income (in the same way Railcards do).
*yes I know that an evening out return is only available for a part of the day, but wished to use the cheapest off peak ticket available as a comparison to highlight that season tickets, whilst a lot of money on one go may not make the railway the profits people assume.