Night trains disappeared from much of Europe in the two decades after cheap flights arrived.
They have returned on several routes since, for reasons that are only partly environmental.
A replaces a hotel night as well as a journey, which changes the price comparison.
City centre to city centre also removes two airport .
The operating economics remain difficult.
A sleeping carries a third of the passengers of a seated one and costs more to clean.
Staff must be paid for the whole night, and a train cannot be used again the next morning.
Track access charges are per kilometre and take no account of the hour.
A night train therefore pays the same for a line that would otherwise be empty.
Two policy changes have made the difference where services returned.
Reduced night charges recognise that the would not be sold anyway.
Public purchase of the s removes the largest cost from the .
Neither is a subsidy for travel; both are a correction of how the track is priced.