Overnight rail services across Europe contracted for years and have since expanded again. The reversal rests on specific changes in rolling stock, network access and the economics of competing modes.
Why they declined in the first place
Sleeper trains carry few passengers per carriage compared with seated services, because a berth occupies far more space than a seat.
They also use expensive assets overnight, when maintenance work traditionally closes sections of track, and they require staff on board through the night.
As short-haul air fares fell and high-speed lines shortened daytime journeys, the overnight product lost its advantage on many corridors simultaneously.
Rolling stock was the binding constraint
Existing sleeper carriages were ageing and no longer met contemporary expectations for privacy, accessibility or comfort, and no manufacturer was building replacements at scale.
Ordering new stock requires a long commitment, since design, approval and delivery take years and the vehicles must be authorised in every country they will run through.
Operators that placed such orders effectively decided the sector's future, because without modern carriages the product could not be relaunched credibly.
Cross-border operation is administratively heavy
A night train typically crosses several networks, each with its own signalling, electrification and safety rules, which the locomotive and crew must be certified for.
Track access charges are levied by each infrastructure manager, and a long overnight run accumulates them across the whole route.
Opening of the market to competing operators has made it possible for newcomers to run such services, though the certification burden remains substantial.
Demand changed as well as supply
Growing attention to the emissions of short-haul flying made an overnight rail journey attractive to travellers who previously chose on time alone.
The overnight journey also converts travel time into sleeping time, which competes with an early flight plus a hotel night rather than with the flight alone.
Comparing on that basis changes the outcome on many city pairs, particularly where the airports sit far from the centres.
What the product looks like now
Modern services separate seats, couchettes and private compartments, with the price gap between them reflecting the space each occupies rather than the service level.
Networks are being built as connected routes rather than isolated services, so that a single overnight leg links into daytime high-speed services at each end.
Capacity remains limited relative to demand on popular corridors, which is why booking well ahead matters more here than on daytime trains.