Show HN: Luna Rail – Treating night trains as a spatial optimization problem

[ant6n]

Hi HN, I'm Anton, founder of Luna Rail.

I've always thought night trains are a fantastic, sustainable alternative to short-haul flights, but they're often held back by a lack of privacy, comfort, and poor economics due to low passenger capacity.

I became overly fascinated with this puzzle. I view it as a kind of night train Tetris (my wife less charitably calls it "sardinology"). I spent way too much time learning about and sketching various layouts, trying to figure out how to fit the maximum number of private cabins into a standard railcar, while making them attractive for both day and night travel.

This eventually led to a physical workshop (in Berlin) and a hands-on rapid prototyping process. We've built a series of full-scale mockups, starting with wood and cardboard and progressing to high-fidelity versions with 3D-printed and CNC-milled parts, with various functional elements.

Hundreds of people have come in to test our various iterations, because you can't test ergonomics or comfort by looking at renderings (although we did create a bunch of nice ones).

The link goes to our home page showing our approach and some of the thinking behind them. It’s been a lot of fun working on this puzzle, and we're excited to share what we've come up with. We hope you think it's cool too and would love to hear your thoughts.

[Freak_NL]

Sleeper trains are held back by flying getting subsidised heavily by not having kerosene taxed, and national governments giving airports effectively unlimited room to grow; happily externalising the environmental cost. Why take a train if you can fly for a fraction of the cost?

Trains in general are held back by governments not investing in rail infrastructure, because the pork barrel of another motorway link is so hard to resist (and we're not properly maintaining these either).

Sleeper trains are held back, because cross-boundary collaboration between the various semi-national rail companies is tough (for Europe).

Sleeper trains are held back, because there is a lack of modern rolling stock. Not completely new concepts; just up-to-date sleeper wagons (the ÖBB has the leading edge here now with their new wagons).

There is room for improvement in the wagon designs, but it is almost irrelevant in the face of the other challenges.

[Saline9515]

I took sleeper trains in France when I was younger, it was quite modern (2000-ish trains), but not a good experience honestly. You have to share a tiny room with 3 other strangers, you are stressed about a possible aggression and/or theft and/or bed bugs, everything is impractical, your neighbor may snore, you can't really take a shower... and I can imagine that a woman can feel very unsafe there, too.

I can see the appeal for young people who want to stay in hostels to save money, but honestly I prefer to drive or take a plane. Money here is not the problem.

[ant6n]

You start off by essentially claiming the unit economics of night trains being too poor compared to aviation is the largest hurdle, then finish off by claiming that unit economics are not that major issue.

Our perspective is that with much improved unit economics, the problem overall becomes much more easily solvable. You can compete with aviation on price. You can pay for prioritized track access. You can operate trains privately without direct involvement of national operators.

Finally, the refurb approach skirts the rolling stock bottle neck.

[gruez]

>Sleeper trains are held back by flying getting subsidised heavily by not having kerosene taxed

Is whatever fuel trains use taxed? If not, I don't see how this is relevant.

>and national governments giving airports effectively unlimited room to grow

Which countries are those? For instance in UK they wanted to expand Heathrow since as early as 2006, yet due to various government shenanigans isn't due to complete until 2040, assuming it doesn't get backtracked again.

https://en.wikipedia.org/wiki/Expansion_of_Heathrow_Airport

Moreover since you're comparing against trains, don't trains need land as well, for the tracks and stations? Why do trains seemingly get a free pass from you on that?

>Trains in general are held back by governments not investing in rail infrastructure, because the pork barrel of another motorway link is so hard to resist (and we're not properly maintaining these either).

What makes motorways more of a "pork barrel" than train tracks?

[bluGill]

You missed a couple other points against night trains.

first trains work best if they stop many times - how will you wake people up at 3am for their stop? For that matter who would agree to that? Without that churn many destinations are not in range.

second, track needs maintenance. If the track is running at night as well when will you repair it? I makes sense to just close nost track every night for repairs. For busy two rail sections you can close on track and run very reduced service on the other - but this reduction means you don't want people sleeping as you can fill your trains just on people working night shifts.

all of the above are challenges. They can be worked around in various ways however they to be considered to see if it is worth it-

[econ]

I've long joked that modules should be made easy to swap with a forklift. Trains are usually full of small defects that aren't serious enough to take them out of service.

If they are comfortable you could rent out the cabins when not in use either fitted on the train or not. You could also retire the units there.

You could make a platform only and make it easy for others to design modules in a broad price range. Maybe most modules should be in storage until booked.

You could park the "hotel" module on the destination and put it back on the train for the return trip.

[ant6n]

I sometimes her proposals like that, and it sounds kind of attractive - you get into your pod and forget everything until you arrive.

But in a sense, night trains are already like that. Since they can stop at multiple places, you can depart and arrive downtown. In the meantime you’re in your cabin and forget everything.

Entering the train „with“ the pod instead of just yourself is gonna make boarding and alighting take forever, and the logistics of storing and moving the pods are a nightmare. It’s going to reduce capacity by a lot because you cannot optimize the layout and every pod needs to be „insertable“ as a whole. (3x reduction in capacity means 3x increase in ticket cost).

Homologation is going to be a nightmare - in Europe, realistically, it’s gonna take more than 10 years or develop something like that. You need a new infrastructure because right now stations are for people - that’ll probably take 20 years (in Europe).

[danpalmer]

> I've long joked that modules should be made easy to swap with a forklift. Trains are usually full of small defects that aren't serious enough to take them out of service.

I assume the implication here is that with more granular swap-outs, you might get more regular maintenance of those minor issues?

While I agree it's a problem and could be improved, I don't find train maintenance any worse than hotel maintenance in general – most hotel rooms aren't in perfect condition and they arguably don't have the same restrictions.

[gregorvand]

Awesome concept and execution.

For those interested, this is a good bbc podcast episode digging in to the economics of train travel including sleeper trains

https://pca.st/episode/262c1fdd-7dbd-4fa2-a3c6-5bf69bae6822

[rmccue]

What do you see as the benefits over Nightjet’s Mini Cabins?

Also, interesting to see just after the launch of https://noxmobility.com/ which is targeting the same market.

[ant6n]

ÖBB Mini cabins

  * night only
  * 40 pods per car
  * implemented

Luna Rail

  * day and night
  * 65 pods or 40 single rooms
  * in physical since 2023
  * team focused on technical development and testing 

Nox

  * day and night
  * virtual concept
  * team very strong on marketing

[graphememes]

the bed looks way more comfortable in this than luna rail

[fyrn_]

Really cool concept. I wish we could have something like this in the US one day.

Wanted to report a small typo, In the 3D model index menu, "Uppder" can be found. I assume this was supposed to read "Upper", as in "above".

I hope to one day ride such a system when I visit europe, best of luck with your project.

[ant6n]

Thanks!

[eqvinox]

Hi! What's your perspective on the shortage of manufacturing capacity for night train rolling stock? Last I heard ÖBB can't build them fast enough for demand, and few other companies are able to actually produce these? Are you planning to build your own industrial manufacturing capability for this? And what about 2nd level suppliers?

[ant6n]

Yes, the bottle Beck for night trains is rolling stock.

The plan is to initially target refurbished standard passenger couches. We have a large research and development consortium to develop the technology and adaptation of coaches.

The refurb itself can be done by many companies, we don’t need a large supplier like Siemens.

As for the ÖBB nightjet, there’s talk about shifting the last ordered nightjet to rail jets (for day travel). Speculation is that the low capacity of the Trainsets result in poor unit economics.

[raybb]

I gotta say I love this? Are you in contact at all with the folks advocating for more night trains across the EU https://back-on-track.eu/ ? Seems like it could be pretty mission aligned.

Btw I run a weekly newsletter about urbanism and while your trains may not be exactly related I think it's cool enough that we'll feature it in the upcoming week! https://urbanismnow.substack.com/

[ant6n]

Yes, we’re connected with back on track! I’m a day-one member of the German branch. A bunch of their members came and participated in our tests.

We’re participating in their night train conference in September in Berlin, probably bringing a physical prototype.

[solardev]

I love the concept and the renders, but I wonder... is the spatial optimization really what's holding train travel back? If you decrease passenger density in order to increase privacy and comfort, do you then have a corresponding increase in ticket prices?

In places with good train travel, it seems like they already have several cabin classes, from sardine seats (still luxurious compared to air travel) to private cabins (at several multipliers of price). Pod style rooms would presumably be cheaper than that, but still a lot more expensive than a seat?

Then in places without high speed passenger rail, like the US, this wouldn't really be able to address the major problems with train travel (slowness, lower priority than freight, low reliability, etc.).

Under what scenarios would using pods instead of cabins be more economically viable? And could these be retrofitted into existing sleeper cars, or would they have to build entirely new trains?

[rocqua]

My experience on the Caledonian sleeper, in a 'room' was quite cramped in all senses (I am over 6 feet tall), and quite expensive aswell. If that had been optimized better, I would have enjoyed it more.

[bruce511]

Clearly different markets have quite different requirements and comparisons to air travel.

For example a "night train" maxes out around 12 hours. A train from 6pm to 6am is functionally equivalent to a 8pm flight, arriving at midnight, checking into a hotel, getting some sleep etc.

How far you can go in that 12 hours (give or take) depends on the speed of the train etc. In Europe you can go to a lot of places in 12 hours. In the US not so much.

Much longer and other factors come into play. You have to balance the time cost of "getting there" to the time benefit of "being there".

But thats OK. This solution doesn't have to work everywhere. It can start where it works well and grows from there.

[ant6n]

You yourself mention the trade off — the „sardine class“ is a six-people per cabin couchette (60 ppl per railcar). The private class is luxury (10-17 cabins per railcar).

We got 65 private pods or close to 40 little single cabins - in a refurbished railcar. In a new car it would be more.

We put together some explanation of the economics and the difference between old and new cars: https://luna-rail.com/approach

[bruce511]

When traveling I often consider trains, and especially overnight trains. It's by far the most comfortable way to travel. Innovation in this space is a good thing.

While I'm aware that feature creepy is the enemy here, I would suggest a way to "combine " two pods for those traveling as a couple. If I'm traveling with my wife we don't want to be in "separate pods".

A retractable "wall" between 2 pods would be fine. It doesn't have to be elaborate, but you wanna point to something outside and say 'look at that' etc.

[ant6n]

We considered connecting pods. The orientation „behind“ each other makes interaction difficult.

They way this issue was „resolved“ more less naturally during testing is that the pods all have The same orientation, so pods across the aisle approximately face each other. In our lab we had two iterations of the pods set up to face each other, and tester and testee interacted quite naturally —- once we set up our test rig like that, the questions „what about couples“ reduced a lot, most understood the vis-a-vis intuitively.

Our bigger cabins have two ppl versions, but a lot (if not most) travel is individua anyway, especially if night trains will be used for work travel.

[MrJohz]

How do you plan to handle groups or families with this system? Having larger compartments gives a lot of flexibility and allows families or groups to travel together easily and spend the time with each other. The hotel pods look like they only go up to two people in size, and the seats are very isolated from each other, not even allowing people to sit next to each other as far as I can see.

I'm excited to see more work being done to improve night train travel though!

[ant6n]

We’re working on standard railcars, which can be running together with traditional couchettes railcars. I would argue that group travel is largely a „solved“ problem, using couchettes (railcars with cabins having 4-6 beds).

For couples, the smaller pods actually kind of „face“ each other across the aisles.

[LargoLasskhyfv]

Interesting. But too blue-eyed/rose-tinted IMO.

Lemme explain. I see no (lockable) doors.

Which means I wouldn't want to let my gadgets and other luggage out there in the open, when having to use the bathroom, or maybe going into the (snack)bar, if there is one.

Which means having to carry my backpack/suitcase around with me, which is annoying.

Which also opens the questions of other commonly encountered annoyances.

Dirty bathrooms/toilets.

What level of service is to be expected, regarding this?

[L_226]

Hello! happy to see this on HN, I tested some of your mockups last year. How are you progressing now, do you see potential collab / competition with Nox? Kind regards,

[ant6n]

Our prototypes keep getting better, and we’re assembling a team of partners for development.

I think it would be great to have more partners in the team, we’re fairly open as to who, if we can make our work better.

[nylonstrung]

Love this idea, I 100% will use it when it is live.

[ant6n]

Thank you!

[PaulRobinson]

Great work so far, but I note you are looking at a custom double-decker railcar with what looks like a very large loading gauge. My understanding is that for most of Europe, double deckers are not used due to loading gauge limits imposed by tunnels, bridges and so on. I presume your planned routes take that into account? Is that one of the reasons your mocked journey planner app doesn’t include the UK?

[nic547]

I'm not sure if that's just my narrow view of europe, but most european railways seem to run double decker trains (albeit not on all lines). Switzerland, Germany, Austria, France, Italy, the Netherlands, Belgium, the Czech Republic, Slovenia and Hungary are the countries I can recall using double deckers with only the UK being generally unable to use them.

[matt-p]

The UK has adequate loading gauge for double deckers on HS1/Chunnel and HS2 (though I'm not sure if the Euston extension will support it or not).

We can run London - Europe double decker today and if we connected HS2 to HS1 it would probably be possible to run from Birmingham, Crewe and Manchester to continental Europe too.

[ant6n]

The „current“ concept is for refurbished standard passenger coaches, which is compatible everywhere in Europe except UK.

The „long term“ concept is built around to be compatible with profiles UIC GB and G2, which work in most of Europe.

[herbst]

We have them in Switzerland. Often had to change train at the border and never thought it could be a technical limitation.

[torwag2]

Whatever you do, add ventilation and if you think you have added enough, add some more. If you do not believe me, go and visit some of Tokyos capsule hotels close to the party districts. Nothing is more worse than the feeling to breath what has very recently left intoxicated people from one or the other side. Also for the sake of avoiding drama on those trains, add snoring tests.

[ant6n]

As a startup, there are two perspectives on these kinds of issues: just get something built and running as quickly as possible, or make sure you work out the kinks.

So far we've been very much doing the second. Built it, experiment on it, test it, make sure it works. Only publish what's actually feasible. Set up more projects to make sure all the kinks will be worked out. Work together with experts to ensure proper ventilation, noise and vibration control, etc. etc.

But as a startup, this process can be frustratingly slow. I am concerned investors may want to see quick results, not perfected solutions.

[ViscountPenguin]

What's up with the super high carbon intensity estimate of your trains? Is it because they're running at night and can't use solar? Does it include embedded carbon in the train? Or is Germany's grid just that dirty?

[ant6n]

15g/km is very low. The number is dominated by energy mix and infrastructure. Deutsche Bahn publishes lower number, but they only look at operation (not infrastructure), and assume „green energy“ rather than the energy mix of the country.

The 15g is a good estimate, see discussion here: https://back-on-track.eu/de/klimawirkung-von-nachtzuegen-neu...

[solardev]

Where do you see the carbon intensity? I just see a plane above a train with a single "250g" figure.

[octo888]

Looks like some heavy inspiration from modern airline business class cabins? Love it

[VoidWhisperer]

I feel like I'm missing something here but even after looking at the 3D view I can't figure it out - how are people meant to get into and out of the upper pods in the private seats?

[ant6n]

There are three ladder steps, and two bars to hold onto while stepping up. From the uppermost step you can already sit on the upper seat.

It’s definitely easier to get into than the öbb mini cabins, because the relative orientation of steps and entrance are better.

[schmorptron]

Cool idea! Small typo on the landing page, in the media section it says "german nationa media" without the l

[ant6n]

Thanks!