Sure, but the best-guess calculation is that it's going to be worth that £50 billion in terms of economic return for the country (even if not all of that is realized as revenue for the government/train operator). But night trains can't be justified even with that kind of logic, only on some kind of social "it's good for people to be able to travel even if it's not economically reasonable" grounds.
Most trains in the UK, and to my knowledge all high speed trains, are electrified, and your link states that electrified services are not subject to this duty.
Not even all the main lines in the UK are electrified, and there's still a large stock of 1970s diesel "High Speed Trains" (yes, that's the actual model name) in operation on main lines.
The main lines:
- Cross Country Route: partially electrified;
- East Coast Main Line: fully electrified (but a number of services continue north of it, which is not electrified);
- Great Eastern Main Line: fully electrified;
- Great Western Main Line: partially electrified (for the first 11 of 120 miles);
- High Speed 1: fully electrified;
- Midland Main Line: partially electrified (again, only for a relatively short distance near the London end);
- West Coast Main Line: fully electrified.
That's 3 out of 7 main lines that are only partially electrified. If we get off the main lines (and quite a number of smaller lines still have frequent services, all diesel!).
Are night trains relevant? No-one builds a railway to run night trains, but once you have the route built for the daytime services, running an extra train at night on an otherwise-empty track must be very low cost business.
Some UK train franchises even lay on so-called 'ghost trains' [1], services that are on useless routes and useless timetables, simply so that they can make up the numbers to hit their service agreements (and so not lose their franchises). This strongly implies that the cost of rolling an extra train along the tracks is relatively small.
> No-one builds a railway to run night trains, but once you have the route built for the daytime services, running an extra train at night on an otherwise-empty track must be very low cost business.
The operators find them unprofitable (at least in the UK). AIUI they can be very disruptive to track maintenance (particularly given modern safety regulations[1]); they also require paying staff, keeping stations open during the night, leasing nonstandard carriages that can't be used for anything during the day (which in turn means either dedicated locomotives or careful scheduling and shunting, something that modern railways try to eliminate as much as possible). Certainly the sleeper train to Scotland is heavily subsidized and I believe the one to Cornwall is as well (less confident of that though). With Eurostar, AIUI the government even bought and fitted out sleeping carriages in the early days of the channel tunnel, before they turned the whole thing over to a private company to operate - which then concluded that night services would be uneconomic, and sold the carriages off cheaply to Canada.
The ghost trains you link to are more about a legal obligation; even if they cost the relevant companies a lot of money to run, they don't have any alternative. (And honestly an off-peak daytime service, when the trains are already out and the staff already on shift, isn't really comparable).
[1] Which are not unreasonable IMO - people have been killed by e.g. a train on the track next to the one they were working on.
It's not about making up the numbers, but because closing a line is an expensive and lengthy affair due to the amount of consultation that is required under the Transport Act 1962
Does the UK have dedicated passenger train tracks?
In the US, most train tracks (in my experience, at least) are used for both freight and passengers (and frequently owned by the freight companies, who shaft the passenger trains to keep the freight running on schedule, but that's another rant). The freight trains could easily be crowding out the night passenger trains.
The UK network prioritises passengers over freight in almost all circumstances. Much of the freight is "bulk" that can tolerate delay quite happily.
You don't see a lot of freight going past while waiting on a passenger platform or at a level crossing. There are some freight-only lines mostly for coal to power stations.
