European Night Trains: the how and the where

This guide to taking an overnight train in Europe includes the routes still taken by night trains, insights as to what you can expect on board and an explanation of how the ticketing works.

The romantic view of overnight train travel; opening the blinds following a restful sleep and seeing a stunning landscape outside the window, can still be a reality on some overnight trains.
But the appeal of taking a contemporary European overnight train is primarily practical - they’re still often the only means of arriving in a city by train before mid-morning, and between many European cities they’re the only direct trains.

If you're new to taking overnight trains there is a weight of useful info, which you may not be aware of.

As will become clear when you read the guide, the travel experience can vary between specific types of train, so what we have focused on here are the general points that are universal.
In particular we have striven to include the less obvious aspects of travelling by European overnight trains.

(1) There are in effect now two types of overnight train which operate in Europe:

• Sleeper trains on which you 'sleep' in a bed or a bunk because these trains convey sleeping cabins and/or couchettes; though coaches which only have seats are often attached to these trains. (Most of our notes below refer to these types of trains).
• Trains which are mainly used for daytime services, so have no sleeping cars or couchettes, that now also travel through the night on some routes; particularly within, and now to/from Germany.

(2) Unless you’re travelling in a group or as a couple and have therefore booked every bed in a multiple occupancy sleeping cabin, or every berth in a couchette, you’re likely to be sharing your overnight accommodation with others, who you will meet for the first time when boarding the train.
Though on some services, if you book the equivalent of a First Class ticket for a sleeping cabin with multiple beds, you will have sole occupancy.

(3) Travel in a couchette and you'll sleep on your bunk in your daytime clothes, so couchette compartments can be mixed sex - some trains including OBB Nightjet trains and SJ Night Trains have female only couchette compartments, but most others don’t.

It can be a great way of meeting new travellers and swapping tips and info, but finding yourself in a couchette compartment with like-minded travellers, or other people using a rail pass etc, is not guaranteed.
If you do baulk on meeting the other travellers in your compartment, you can have a discreet conversation with the conductor, to see if you can move compartments or be swapped with other passengers.
But the chances of success in this scenario are not guaranteed.

Never assume that what looks like an alternative berth in a different compartment or cabin, will remain free for an entire journey.

(4) A factor for sleeping cabins being more expensive than couchettes is that the beds in sleeping cabins are fully made up, the idea is that you get ready for bed as you would in a hotel.

If you wouldn’t do this when sharing your multi-bed sleeping cabin with a stranger, so would prefer to remain in your daytime clothes, compare the cost of a cabin with a couchette.
You will be partially paying a premium in order to get into a bed, so if you don’t, you could have made a saving if you had opted for a couchette instead.

(5) Multi-bed sleeping cabins are segregated into male and female cabins.
However couples are allowed to travel together in a two bed sleeping cabin and families can travel together in a multi-bed cabin.

Below is a list of the primary European international night train routes; as will be seen it's quite lengthy, reports of the death of European night trains have been a tad exaggerated.

Also note that specific types of trains are assigned to only some routes, some European night trains particularly in eastern Europe don't fall into the Nightjet and EuroNight categories.
Those marked with * are the only direct train services between cities at each end of the routes.
The trains make additional calls to those listed below.
Click the city names, when available, to access journey guides to taking a route, which include specific ticketing info.

Nightly routes:

• Berlin <> Przemysl (for connections to/from Lviv)
• Munchen/Munich ↔ Firenze/Florence* - Roma* by Nightjet
• Munchen/Munich ↔ Ljubljana and Zagreb by EuroNight
• Munchen/Munich ↔ Wien/Vienna – Budapest by EuroNight no sleeping cars available for the time being
• Munchen/Munich ↔ Udine – Venezia/Venice by Nightjet
• Munchen/Munich ↔ Milano – by Nightjet
• Innsbruck – Munchen/Munich ↔ Hannover – Hamburg by Nightjet
• Innsbruck – Munchen/Munich ↔ Amsterdam by Nightjet
• Praha/Prague - Warszawa/Warsaw <> Minsk - Moskva/Moscow (currently not travelling beyond Warszawa)
• Praha/Prague - Krakow/Cracow
• Zurich ↔ Wien/Vienna – Budapest by EuroNight no sleeping cars available for the time being
• Zurich ↔ Wien/Vienna by Nightjet
• Zurich ↔ Graz by Nightjet
• Zurich ↔ Ljubljana – Zagreb by EuroNight
• Zurich – Basel ↔ Berlin* by Nightjet
• Zurich - Basel ↔ Hamburg by Nightjet
• Zurich ↔ Prague*
• Wien/Vienna – Linz ↔ Koln/Cologne and Amsterdam by Nightjet
• Wien/Vienna – Berlin by Nightjet
• Wien/Vienna – Linz ↔ Hannover – Hamburg by Nightjet
• Wien/Vienna ↔ Firenze/Florence* - Roma* by Nightjet
• Wien/Vienna ↔ Verona* - Lake Garda* - Milano* - by Nightjet
• Wien/Vienna - Linz ↔ Udine – Venezia/Venice by Nightjet
• Wien/Vienna ↔ - Krakow - Warszawa/Warsaw by EuroNight
• Wien/Vienna - Budapest ↔ Kiev* suspended until further notice
• Wien/Vienna - Budapest ↔ Buccuresti/Bucharest* by EuroNight
• Sofia ↔ Istanbul* suspended until further notice
• Budapest - Warszawa/Warsaw <> Minsk by EuroNight (not travelling beyond Warszawa)
• Budapest – Berlin by Nightjet
• Budapest ↔ Prague/Prag Nightjet
• Budapest ↔ Beograd/Belgrade suspended until further notice due to works on the railway.

Certain nights of the week only and Seasonal services:

• Bruxelles and Liege ↔ Linz and Wien/Vienna by Nightjet
• Budapest ↔ Ljubljana
• Beograd/Belgrade ↔ Zagreb - Ljubljana*
• Bucuresti/Bucharest ↔ Istanbul* suspended until further notice
• Bucuresti/Bucharest ↔ Sofia*
• Bucuresti/Bucharest – Sofia ↔ Thessaloniki* suspended until further notice
• Paris ↔ Warszawa/Warsaw – Minsk – Moscow/Moskva* suspended until further notice
• Nice ↔ Warszawa/Warsaw – Minsk – Moscow/Moskva* suspended until further notice
• Berlin - Warszawa/Warsaw ↔ Minsk – Moscow/Moskva* suspended until further notice

This information has been taken from the European International Rail Timetable.

What is the difference between a Nightjet and a Euronight train?

Nightjet Trains:

These are trains operated by Austria’s national rail company, OBB, and it sets a specific and consistent standard of service for these trains on its domestic and international routes.
All international Nightjet trains convey compartment seats, couchettes, standard sleeping cabins (no showers) and deluxe sleeping cabins (with showers).
Nightjets also have a dedicated section on the OBB website.

Euronight Trains:

In contrast, ‘Euronight’ trains are more varied as they are operated by multiple national rail companies, which also explains why there is no Euronight website.
The branding was originally used as an indication that ‘Euronight’ services were superior to other alternative other night trains.
Though in reality this could mean that a Euronight train included sleeping cabins, when other trains didn’t.
Over time those other services have been discontinued, leaving the Euronight trains as the only remaining trains on many routes.

Not all overnight European trains are international, so here's a summary of the main domestic routes:

France:

On Friday - Sunday nights only Intercités De Nuit trains operate between Paris and multiple destinations in south west France, including Aix-Les-Thermes Carcassonne, Gap, Perpignan, Port Bou (for connections to Barcelona) and Rodez.
These trains convey couchettes, reclining seats and ordinary seats, but not sleeping cabins.

Germany:

In Germany the ICE trains, which are mainly used on daytime services, also operate overnight on these routes:

• Munchen/Munich ↔ Berlin
• Munchen/Munich ↔ Frankfurt (Main) - Koln/Cologne - Essen - Dortmund
• Berlin ↔ Koln/Cologne

Regular IC trains operate overnight on these routes:

• Hamburg - Hannover ↔ Heidelberg - Karlsruhe - Baden Baden - Offenburg - Freiburg
• Hamburg - Bremen ↔ Mainz - Frankfurt (Main)

Nightjet trains operate between these cities:

• Berlin ↔ Karlsruhe - Baden Baden - Offenburg - Freiburg
• Hamburg - Hannover ↔ Karlsruhe - Baden Baden - Offenburg - Freiburg
• Munich/Munchen - Augsburg ↔ Hannover - Hamburg
• Munich/Munchen - Augsburg ↔ Frankfurt (Main) - Mainz - Koblenz - Koln/Cologne - Dusseldorf

Great Britain:

(1) London - Reading ↔ Plymouth - stations in Cornwall - Penzance on the Night Riviera

(2) Caledonian Sleeper trains operate between London and multiple destinations in Scotland including Aberdeen, Dundee, Edinburgh, Fort William, Inverness and Perth.

Italy:

Trenitalia operates 'Treno Notte' overnight trains on these routes; the ↔ symbol indicates which part of the journey is overnight.

(1) Roma ↔ Trento - Bolzano

(2) Roma ↔ Venezia/Venice - Treviso - Udine - Trieste

(3) Roma - Napoli ↔ Messina - Palermo and Siracusa

(4) Milano - Genova - La Spezia - Pisa - Livorno ↔ Messina - Palermo and Siracusa

(5) Torino - Milano - Genova ↔ Napoli - Salerno

(6) Torino - Milano - Bologna - Firenze - Roma ↔ Villa San Giovanni - Reggio di Calabria

(7)Torino and Milano - Piacenza - Parma - Modena - Bologna - Rimini ↔ Bari - Lecce

Norway:

NSB operates Sove trains on these routes:

• Oslo ↔ Bergen/Stavanger/Trondheim
• Trondheim ↔ Boden - Narvik

Sweden:

SJ Night Trains operate on these routes:

• Stockholm - Uppsala - Galve - Sundsvall ↔ Boden - Kiruna - Narvik
• Malmo/Gothenburg - Stockholm ↔ Ostersund - Are
• Malmo - Stockholm
• Gothenberg↔ Ulmea - Boden - Luléa
• Stockholm - Uppsala - Galve ↔ Ulmea - Boden - Luléa

A couchette is a self-contained compartment on a train with a door to a corridor.
During the day it has two sets of three seats, which face each other, but at an appropriate time the conductor will convert the compartment for night use.
The seats become beds and more beds, which had been folded away, become bunk beds - a pillow and a sheet will be placed on each bunk.
Though it’s quite likely that when you board the train that the compartment will already have been converted for night time use.

Six Things To Know About Travelling in a couchette

(1) A key difference between travelling in a couchette and a sleeping cabin is that travellers in couchettes sleep in their daytime clothes; you simply hop on your bunk when it’s ready.

(2) Also washing facilities are always only available at the end of the train corridor outside of the cabin.
Though the WCs on couchettes cars are little different to the WCs that will be available on daytime trains; meaning that the sinks are next to the toilets.

(3) As passengers remain in their clothes, couchette compartments are often mixed sex, though OBB Nightjets and SJ Night Trains offer women only couchettes.

(4) Couchettes can be 4 berth or 6 berth, with tickets for 6 berth compartments being cheaper when both types are offered.
The top bunks in a 6 berth couchette are usually very close to the ceiling of the compartments.

(5) Couchettes are more basic (and less comfortable) then sleeping cabins, so they’re also much cheaper.

(6) If you’re travelling in a group of 6 people or 4 people and want to reserve an entire compartment, you need to do so at the earliest opportunity.
If you’re in a group of less than 4 or 6 people, it’s likely that you’ll be sharing a compartment with people that you don’t know.
It can be a great way of making new travel companions and swapping tips, but be aware of security and keep valuables hidden and locked if possible.

A key distinction between couchettes and sleeping cabins, is that the bed/bunks in sleeping cabins are fully made up, as they would be in a hotel, the bedding is prepared by the attendant on the train.
You can get ready for bed as you would if you were staying in a hotel, and then get into the bed between the sheets.

Eight Things To Know About Travelling in a sleeping cabin/compartment

(1) If you will be making an international journey in a sleeping cabin, you will hand your passport, tickets and other travel documents to the sleeping car attendant, when you board the train.
Then when the train crosses a border, the attendant will deal with the border staff on your behalf, thereby ensuring that you're not disturbed in the middle of the night.

(2) The beds are usually more comfortable and slightly larger than the berths in couchettes, though the difference can be marginal.

(3) In most sleeping cabins the beds are placed vertically, bunk style; as they are in couchettes.

(4) The majority of beds in sleeping cabins on European overnight trains will be single beds, they can rarely be converted into doubles - though double beds are available if two people are travelling together on the Calednonian Sleeper trains between London and Scotland.

(5) The other key difference compared to couchettes is that, unless you book together as a couple or family group, sleeping cabins with more than one bed are segregated into male or female only.

(6) The fewer the number of people occupying the cabin, the higher the ticket price, but when travelling alone consider you are very likely* to be sharing a multiple bed cabin with someone you have never met before.
Unless you will travelling in a group/family, which has reserved every bed in the cabin.

*The train operating companies understandably attempt to ensure that the only travellers with a cabin to themselves, are those that have paid a premium to guarantee their privacy.

SJ Night Trains are an exception to this rule - on those trains if you book a bed in a 1st class cabin and will be travelling alone, you will have sole occupancy according to the SJ website.

Also if you make a booking for one person, for the types of multi-bed cabins on the new Caledonian Sleeper trains, you won't be sharing the cabin, but will be paying the full reservation cost for the cabin.

On the Intercity Notte trains in Italy the reservation fees are also based on the cabin and not the beds, so places are automatically assigned according to how many people are travelling together.
Therefore if you travel alone you will be the sole occupant of which ever type of cabin you opt for, but will have to meet the full reservation cost of the cabin (or couchette compartment.

(7) There is USUALLY little difference between a single bed cabin and multiple bed cabins in terms of facilities offered.
When you pay a premium price to travel in a single berth cabin, or to have sole occupancy of a multi-bed cabin, you will primarily be paying for the privilege of not having to share it with anybody else.
The other beds in the cabin will usually be folded back or simply left vacant.

(8) The difference between 1st and 2nd class is not universal.

On some trains/routes the key difference between the equivalent of 1st and 2nd class is how many people will be occupying the cabin; 1st class = 1 OR 2 people; 2nd class = 3 or 4 people.
On other trains the equivalent of 1st class means that there will be a shower available in the cabin, and 2nd class indicates there won't be.

However, this is fluid as many night trains often don't use 1st and 2nd class terminology.

Though if you travel 1st class, or the equivalent you'll usually receive other benefits, which can include more generous breakfasts, complimentary washing kits and access to 1st class lounges at stations.

Aside from the beds what other facilities are available in a sleeping cabin?

This varies depending on the train/route, but these three things are universal:

1: What you won’t find in a sleeping cabin is a TV, minibar/fridge etc.
2: Not all sleeping cabins have WCs in the cabin, though those that are classed as Deluxe or Premium will have them.
3: Some form of washing facility will be available in the cabin, but it may only be a basin; showers are the exception rather than the rule.

Also worth knowing:

• This may seem a tad bizarre, but sleeping cabins are often categorised depending on the washing facilities available in the cabin.
• On certain routes, including most Nightjet services, some sleeping cabins have sinks/basins, while others also have showers.
• On trains when BOTH types of cabin are offered, the cabins with a shower are classed as Deluxe or Premium class etc and are inevitably most expensive of all.

On some overnight routes within and to/from Germany, travelling in a couchette or sleeping cabin isn't an option.
That's because the same trains that are used for daytime IC services, now also operate on some routes.

Most other European overnight trains offered seated accommodation, because coaches which only have seats are attached to the coaches which house the sleeping cabins or couchette berths - though exceptions include Thello and SJ Night trains.

The types of seats on night trains:
(1) Standard daytime coaches with open plan seating, which are attached to the overnight train - this the norm when daytime IC trains are also used for overnight services.
On many overnight trains to/from Germany these overnight standard coaches are branded as 'IC services' and on some routes the IC trains are now being combined with Nightjet trains.
(2) Reclining seats, these are available on the Caledonian Sleeper services.
(3) Seats in compartments with a door to a corridor.

The seats in these compartments can, in theory, USUALLY be pulled together flat to create a sort of bed, similar to how you fold down the rear seats in a car.
Though this type of compartment is becoming the exception rather than the norm.

However, to make use of this facility you need to have a spare seat opposite to yours. The compartments have six seats, but only a maximum of three adults can lie on the seats when they’re pulled flat; cosy!
So don't assume that you can make big savings on couchette/sleeping cabin prices and still have a bed for the night.
If too many seats are occupied then converting them into beds won't be possible, though you can try asking people to move seats, if you're desperate to get your head down.

Also if you have lucked out and made a ‘bed’ don’t expect to sleep on it all night.
As many overnight trains approach their destinations, they become early morning commuter trains, so it’s likely that you will have to make room for other people who will be joining the train.
The train conductors also tend to strive to make sure as many seats are available as possible at all times, so you may be abruptly woken in the middle of the night.

Even if you can make a 'bed' a good night's sleep isn't guaranteed. A friend who made several journeys in one of these 'beds' and then switched to a couchette for another journey has said that the 'couchette' felt like The Ritz' in comparison!

On most overnight train routes the era of having a meal in a restaurant car and then retiring to your bed for the night is in the past, the Caledonian Sleeper trains is a notable exception.

On some train services complimentary bottles of water are provided to all passengers and on many (but not all) overnight trains, a complimentary breakfast is served to the travellers in the couchettes and sleeping cabins.
On some services/routes a more generous breakfast tray and tea/coffee, similar to what you would expect on an airline, is brought to the passengers in the sleeping cabins.
When available, the complimentary breakfast served in the couchettes can only be a croissant and bottle of water.

If will be travelling in a sleeping cabin on OBB Nightjet trains, a menu of non-complimentary snacks and drinks is available, so you can order from the conductor and have items delivered to you.
Other overnight trains have vending machines that sell drinks and snacks.

On Italian Intercity Notte trains, a catering attendant will take a trolley through the entire train.

However, taking your own food/drink on board with you is often a good idea, particularly if you will be travelling in the seats or a couchette, or if your train will be departing in the evening and not late at night,

If you travel in a seat or a couchette the washing facilities will be in the equivalent of standard train toilets, so the appeal of using them in the mornings can be diminished.
Therefore another plus of using sleeping cabins, is that the MINIMUM facility in the cabin will be a sink/basin.
So you won’t have to share it with anyone else other than your fellow occupants of the cabin; if you have any.

The ultimate luxury is the availability of a shower in the cabin, though privacy can be a tad limited.
Also cabins with showers are not available on all routes, many ‘EuroNight’ services don’t have them.

Overnight train tickets differ from daytime train tickets because there are two elements to how the price is calculated:
(1) the charge for making the journey AND
(2) a reservation charge for the type of accommodation you will be travelling by.

This journey price is usually the price of travelling in a seat.
What percentage of the total cost is covered by the reservation charge can vary; it tends to be lower in Eastern Europe.

Four Things That Are Good to Know About Night Train Tickets

(1) On many booking services this cheapest seat price will be the first price displayed, you will only see the prices of travelling in a couchette or sleeping cabins, after you have initially clicked on this seat price.

(2) Some ticket booking services (such as DB) combine these journey and reservation prices, but on others (including OBB) you add the reservation fees for travelling in a sleeping cabin or couchette to your booking.

(3) If you will be travelling in Eastern Europe there may be no difference in price between booking online, or at the station; or the price difference can be the equivalent of only a few euros.

(4) Tickets to travel on most overnight trains, including all those in Western Europe, can now be booked online and there are two big pluses for booking in advance;

1. You can increase your chances of travelling in your first choice of accommodation.
   Some types of accommodation can sell out days (even weeks) in advance, particularly in the summer months.
   So if you want to travel in a couchette or a particular type of sleeping cabin, try to avoid booking last minute at the station.
   (Though the full choice of additional fees for single occupancy etc can be hard to track down on some online ticket sites).

2. On many routes, limited numbers of advance discounted tickets are available, as they are on day trains, so when these tickets have sold out the price rises.

What can be less clear cut is whether taking an overnight train will save you money compared to spending a night in a hotel or hostel?
A broad answer is that the ticket price (journey + reservation fee) of travelling in a couchette is usually more expensive than a shared room in a hostel, and a 1 bed sleeping cabin is more expensive than a typical 3-4* hotel room

These seven things are particularly worth knowing:

(1) If you want to travel as a couple or family in a sleeping cabin, take care when booking online.
If you have only been given the option to enter ‘male’ or ‘female’ during the booking process, you can find that you’re booked into separate cabins; some booking systems won’t assume that you want to travel as a couple.

(2) Avoid gambling on booking a multi-occupancy sleeping cabin and assuming that you may have it to yourself.
This scenario is very unlikely as it is the train operator’s interest to ensure that those who have paid for the privilege to have a cabin to themselves, are then the only people on the train who have that luxury.
Though individuals who book a bed in a 2 bed 1st class sleeping cabin on a SJ Night train, or in a 2-bed cabin on a Caledonian Sleeper train will have sole occupancy

(3) There is USUALLY a big price difference (€40+) between a two bed sleeping cabin and a single bed/occupancy cabin.
Unsurprisingly most solo travellers don’t relish the prospect of sharing a ‘bedroom’ for the night with a stranger.

However, book a single cabin and you will be primarily paying a premium for your privacy.
The bed and cabin won’t usually be any larger or any more luxurious.
More often than not, single bed cabins are no different to other sleeping cabins, the other beds in the cabin will usually be stowed away or left vacant.

However, yet again the Caledonian Sleeper trains are an exception to this, none of its sleeping cabins have more than two beds, but its Club Rooms (cabins) are more luxurious than its Classic Rooms, partially because the Club Rooms have an en-suite shower.

(4) In addition to the journey price, the reservation fee for a single bed/occupancy cabin without a shower will typically cost more than €90; with a shower in a cabin the price is typically more than €120.
As you’d expect when sleeping cabins with a shower are an option, they’re more expensive than standard sleeping cabins, but you will be primarily be paying this premium price in order to have a shower.
The Deluxe/1st class/’Premium cabins aren’t usually otherwise more luxurious than the standard sleeping cabins.

(5) If you generally fall asleep when travelling long distance on a daytime train, there are coaches with ‘day’ seats attached to many overnight trains.
You may got more sleep than you would in a couchette and you will typically save around €25, by only paying a reservation fee for the seat, rather than a couchette

(6) When booking tickets at a station booking office be clear whether you want to travel in sleeping cabin, couchette or ordinary seat.
If you don't specify the type of ticket you require, the default tickets that you may be sold may only be valid for travel in ordinary seats.

(7) On many routes, the overnight trains are much slower than daytime trains, they make longer, less direct journeys and they can’t travel on the high speed lines etc.

Nightjet trains have family couchette compartments with 6 berths, which are sold at flat rate price - so are particularly good value if you will occupying 4 or more berths.

Children also travel at discounted rates in sleeping cabins on Nightjets, but the price per bed isn't particularly cheaper - but there are savings to be made if up to two children share a bed.

On other night trains:

The following broad terms and conditions CAN apply to accommodating children in sleeping cabins (not couchettes) on other night trains, but confirm when booking.

• Child up to 4 years without separate bed = free
• Children aged 5-10 without separate bed = no reservation charge, but the ordinary child rate for the journey is charged.
• Children aged 1-10 travelling in a separate bed = full reservation cost for the bed, plus the child rate for the journey.
• Children aged more than 10 years must travel in a separate bed = full reservation cost for the bed charged plus the child rate* for the journey.

*The upper age range for the child ticket will usually be same as applied to child tickets, for journeys in the country in which your journey is commencing.
So the upper age limit for child tickets can vary between 12 and 16.

• Children up to 4 yrs sharing a bed with each other = full reservation fee cost for the bed, plus one half fare for the journey.
• Children aged 4-10 yrs sharing a bed = full reservation fee cost for the bed, plus a minimum of one half fare for the journey - though many operators will apply child rate journey fares to both children.

Think twice if you're considering sharing a bed with your child or having two children share, the beds in sleeping cabins are much smaller than a typical single bed in a hotel.

The key thing worth knowing is that an InterRail or Eurail pass typically only covers the journey element of the costs of taking a ride on an overnight train, so what's not covered are the reservation fees for seats, berths in couchettes or beds in sleeping cabins

Therefore prior to boarding, rail pass users need to pay reservation fees to travel in a couchette or sleeping cabin; and for most overnight journeys this also applies if you want to travel in a seat.
These rail pass reservation fees can be more expensive than those that are included within the price of ordinary tickets.

The rail pass reservation fees are included within our guides to travelling by Nightjet trains and for most of the different types of EuroNight train.
Though if you want to travel in a sleeping cabin, the amount that you will save by using a rail pass, against the total ticket cost can be comparatively small.

Will using a rail pass be good value on a night train?

These three things are worth keeping in mind:

(1) Some good news, particularly if you want to use the type of rail pass restricted to a set number of travel days, is that an overnight journey now only uses one of your allocation of travel days.
Meaning that you can add destinations to your itinerary without using a day of your travel allowance!

(2) If you're happy to travel in the seats then you can go a long way for a reservation fee of €5 - 15; and you could be in luck and convert a compartment seat(s) into a bed.

(3) As rail pass users only have to pay the reservation costs, a berth in a couchette can be comparable to a bed in hostel and a bed in a sleeping cabin can be good value, in comparison to a hotel room.
However, the reservation fees for a bed in a sleeping cabin can be more than €80.

Be open to the possibility, that if you want to mainly travel overnight in sleeping cabins on a pan-European rail travel itinerary, using a rail pass will likely offer comparatively poor value money, compared to the train ticket costs.

How to book the rail pass reservations?

If you will be travelling with rail pass on an overnight train in Western Europe between May and October, then making reservations before you arrive at a station to take the train, is highly recommended.
Leave it to the last minute and you can discover that your first and second choice of accommodation is completely sold out.

A welcome development is that OBB, the Austrian national rail operator and provider of the Nightjet network, now enables rail pass users to book reservations online for any journey by Nightjet PLUS any other night train to/from Austria - how to do this is explained here.

Similarly the Czech national rail operator CD, also enables rail pass users to book reservations online for night trains from and to The Czech Republic - here are the instructions.

Rail pass reservations can be booked by phone for the Caledonian Sleeper services, between London and Scotland

Though the German national rail operator DB has recently withdrawn its online facility for the booking of night train reservations.
If you will be travelling through a major German station, a hauptbahnhof, towards the start of your itinerary, a good option can be booking your night train reservations at a Reisezentrum travel desk.
You won't be charged booking fees and most European night trains can be booked at these desks, including night trains which don't travel from/to Germany.

However, if you want to book reservations before you embark on your rail pass trip and will be travelling on a service/route on which the operator doesn't offer the facility for rail pass users to book specific rail pass reservations online, the only option is to use the Eurail reservation service or the InterRail reservation service - though you will be charged a €2 booking fee per reservation, per person.

Also worth knowing before booking a rail pass reservation:

Whether you have a 1st class or 2nd class pass can make a difference to the type of accommodation you will be able to reserve.

First class pass users can USUALLY trade down and travel in a seat or reserve couchette berths, but MAY have to travel in the equivalent of 1st class sleeping cabins (when multiple types of sleeping cabin are available).
For 2nd class pass users the opposite can apply, having access to single berth cabins, or cabins with showers is usually only available if you will be travelling with a 1st class pass.

But this isn't universal. you can choose any type of accommodation on the Nightjet trains, regardless of whether you have a First or Second class pass; and on these trains, there is no difference in the reservation fees charged to 1st and 2nd class pass users.

Three things in particular are worth knowing:

(1) Most overnight train services commence and finish their journeys joined to other trains.

For example the train that departs every night from München Hauptbahnhof/Hbf at 23:25 is

• the OBB Nightjet train heading to Venezia AND
• the EuroNight ‘Kalaman Imrie’ train heading to Budapest AND
• the EuroNight ‘Lizinski’ train heading to Zagreb.

When this is the case, the departure screens and info displays at stations normally cannot manage this scenario and only show one of the destinations.

Using the above train from Munchen as an example, if you were heading to Zagreb on the train departing at 23:25, you may only see a train heading to Budapest on the departure screens, but the info will also apply to your train, that will be leaving at the same time.
So keep the time of your departure front of mind.

(2) Don’t assume that overnight trains will depart just before midnight and arrive after dawn.
It’s not unusual on routes which only involve one night of travelling, for a train to depart before 21:00 and arrive at a destination before 07:00 in the morning.

(3) It’s also not unusual for trains to make station calls, in the middle of the night, but our advice is to think twice about joining a train after midnight
Most station facilities, including waiting rooms can be closed after 22:30, or even earlier.

Eye masks, ear plugs and taking your own night pillow etc are all highly recommended even if bedding will be provided; in sleeping cabins the rule is one pillow per bed and additional bedding cannot usually be requested.

Night trains can be noisy, the trains don’t travel slowly so that passengers won’t be disturbed.
Also many trains are separated and then joined to other services in the middle of the night, so in early hours expect the noise and sensation of trains being joined together.

If you WON’T be travelling in a sleeping cabin, check whether your destination is the final stop of the train’s journey.
If it’s not you’ll have to set the alarm and make sure you’re up in time to get off the train.
Though if you travel in a sleeping cabin, the attendant will wake you.

If you will be taking a train to its final destination you MAY not have to leave the train as soon as it arrives, so it's worth checking with the conductor, you may be allowed to remain on the train another 30 mins to get yourself ready for the day ahead.