It seems like some people actually like reading my long posts about weirder aspects of the german rail network, so here's another. What is the difference between these three trains?
Well, there's lots of differences, starting with the color and then going on for a long time (I just realised that the white one has a different coupler. No idea why), but the one I'm interested in: In each of these Bombardier Talent DMUs, the middle low floor part is at a different height. The first train (class 643.0 of) has it at roughly 60 cm above rail top. The second (class 643.2 also of DB, with branding for the Euregiobahn network) has it at roughly 80 cm above rail top. The third (of Regiobahn; no class number because that company doesn't have any other trains) goes above and beyond at roughly 1 m above rail top. While a number of trains are available in two heights, the Talent is one of the rare category that has all three, which it apparently managed by cheating: The Regiobahn one has the same carbody as the Euregiobahn one, but some spacers in the trucks appear to raise it higher. The trick to telling them apart, by the way, is the windows: The 55 cm version has the lower middle windows aligned with the bottom of the windows in the door, while the 76 cm version has them aligned with the top of the door windows.
The reason for this is, of course, that the german rail network has a lot of history that left it a bit of a mess in places, and politics ensure that it remains so to this day. The fundamental issue for all these trains is the height of the platforms that they are meant to serve. In Germany, you will, roughly speaking, find four different heights: 38 cm, 55 cm, 76 cm and 96 cm.
This requires some backstory. In the days of old, platforms were just about high enough that they were above the rails. The nominal value for such "classic" platforms is 38 cm above rail head, though you will still find many platforms that are actually much lower than that. As a result, trains in Germany have always had and always required built-in staircases that people had to climb. You can see that staircase below the white doors on this "Silberling"/n-Type carriage:
This was inaccessible to wheelchair users, and very badly accessible for people with a lot of luggage, the elderly and so on, but back in the day people just didn't care. Keep that in mind the next time you hear german rail fans say, "Silberling cars were so much better!".
The 38 cm figure matches, not by accident, the lowest step on that (standardised) staircase. The further heights are then all spaced about 20 cm apart, which means each one removes another step you have to climb up… but increases the gap you have to jump. Again, accessibility is a new topic for railroads.
The 55 cm step is then a compromise position that makes things somewhat easier, but doesn't cause any major gaps either. Many countries throughout Europe have adopted it as their standard, such as Switzerland or France.
From the other side of things, the 96 cm figure was first used on the Berlin S-Bahn, where the staircase would have impeded quick passenger flow. The solution was level boarding, which, at the time, required lowering the car floor a bit, and raising the platform to match, like on the subway networks. The 96 cm figure was then also used in Hamburg and in the first generation of post-war S-Bahn networks (Frankfurt, Munich, Stuttgart).
However, it is expensive and incompatible with normal trains, due to the wide jump. The 76 cm figure then is a compromise: Still reasonable for normal trains, and just a single step for the dedicated suburban trains (again, people at the time assumed that they wheelchairs were someone else's problem). In fact a number of S-Bahn networks were planned and built with 76 cm high platforms but using trains for the 96 cm platforms (with a 1m floor height). The networks in North-Rhine Westphalia and Nuremberg are examples of that… until they rebuilt some platforms in North-Rhine Westphalia to be at 96 cm for better passenger flow, and explicitly giving up on compatibility to normal trains.
Then, in order to improve convenience, DB started building newer trains specifically to the 76 cm standard and started establishing it in long-distance stations. There are still some stairs, but fewer, and you can fill the gap nicely. Apart from a few prototypes, the key example for this is the ICE:
So at the end of the 1980s, the situation was a bit confusing, with a rough "higher is better" idea. But many, especially regional, stations were still at the 38 cm or below, with platforms that increasingly looked like tar patchwork. In that situation, in the early 1990s we got a number of new developments (new for west Germany anyway): First, double-deck trains started appearing. They traditionally come in two versions: Doors over the trucks (
) and doors in the lower portion (
Then we also got the first generation of low-floor single-deck EMUs and DMUs, such as the Talent above. And finally, the responsibility for managing regional traffic fell to the states.
So what height do you pick when ordering new trains and rebuilding your platforms? 38 cm is out, because mainline trains usually cannot be built to be that low. For single-deck trains, the difference between 55 and 76 is kind of irrelevant, you can order them either way. The Talent 2
can actually be rebuilt either way pretty quickly: The floor height is at 65 cm, and at the doors there are ramps either leading down or up to it. These ramps are bolted on and can be replaced easily.
For double-deck trains, the question becomes interesting. The "over-truck" cars work much better with the 76 cm platforms; you still have to climb a few steps there. The cars that have platforms in the lower level, on the other hand, have their floor below platform level either way, just so you can get enough standing space. The doors there have ramps that lead up to the 55 cm level. These ramps can be raised electrically (in some cars at least) to reach the 76 cm level. That means only the "lower level door" cars are wheelchair accessible. As a result double-decker trains in Germany either have mostly "over truck" doors and one (or two, in Lower Saxony) cars with "lower level" doors, or they all have lower level doors. There are no (almost no? None that I'm aware of) trains with all "above truck" double-decker cars, and in particular, in Germany all double-deck cab cars have their doors in the lower level.
That means for double-deck trains, 55 cm is usually the right choice, because it provides the best accessibility. Of course, the lower-level doors means worse passenger flow (because the people in the upper level have to go down more steps, and because the lower level doors are not as wide), so maybe there's something to the 76 level after all? There are actually now a few double-deck EMUs, based on the single cars, that have lower-level entries at 76 cm, which they manage by not having any seats right above the doors; you can recognise them by the small window above their doors.
It works, but you do loose a number of seats, and having a lot of seats is the reason why you go double-deck in the first place. So double-deck generally prefers 55 cm.
Single-deck regional trains can go either way. 55, 76, they don't care, just make sure you check the right box when you order.
ICEs are the last remains of classic high-level trains, and they would really prefer 76 cm. In their case accessibility is ensured via built-in wheelchair lifts in the trains (I actually don't know what the TGV uses, but I think at least the TGV Duplex probably prefers 55 cm).
The one meter (or 96 cm) figure is outdated and new S-Bahn networks (e.g. Hanover, Frankfurt/Main) don't use it, but due to the massive investment in it, it's not going away any time soon in most networks. In some cases new extensions to existing networks will still be built to that standard. This is actually the story behind Regiobahn. Their line, the S28, uses the S-Bahn network (with mostly but not entirely 96 cm platforms) between Neuss and Düsseldorf, and so they decided to buy specially made trains for that height, and built all their own new platforms on the reactivated branch lines at 96 cm as well.
The result is, as you can imagine, a bit of a mess. There's the odd 96 cm network still around. Other than that, lines were either adapted to 55 or 76 cm more or less based on what the long-distance stations in the vicinity already had, or what was cheaper (which will always be 55 cm), or what made sense based on whatever other considerations seemed valid at the time. In the former GDR, 55 cm is basically the existing standard, because it has a long history of using double-deck trains, most of them (and all since the 1970s) with low floor entries. Rural routes are more likely to use 55 cm than ones near major cities, but don't count on that always being true. Some stations have both, to serve different trains, and sometimes even at the same platform with a step in between, such as here at Düren:
The Rurtalbahn RegioSprinter sits at its very own 55 cm section, while the rest is at 76 cm, used mostly for double-deck trains with high-level doors. Düren, by the way, also has a 96 cm platform for the S-Bahn Cologne, as well as some non-rebuilt 38 cm (or lower) platforms also used by Rurtalbahn on the north side, which makes it one of the rare stations (possibly the only, I didn't check) that get the full set.
Obviously this situation is causing problems. Among the more unexpected ones, there's currently a lawsuit from an advocacy group for disabled people against… the Swiss railroad SBB, of all people. Switzerland has 55 cm everywhere and is happy with that, but their newest double-deck trains will also be approved in Germany. Since new regulations mean that the door height must be at most about 20 cm lower than the platform (here's a consideration that railway engineers of old would never have thought possible), the entry must be pretty precisely at the 55 cm level (actually a little bit above). Since the floor is actually much lower than that, this minimum height requires some fairly steep internal ramps. The Swiss advocacy group argues that this ramp is not practical for wheelchair users, so they want these trains changed through legal means. It seems so far like SBB is going to win this one, after loosing an earlier battle with the same group about different aspects of the same train that lead to a massive delay in the programme.
There are now some moves to unify things. For example, the S-Bahn Rhein-Ruhr, the northern part of the S-Bahn network in North-Rhine Westphalia, has decided to settle on 76 cm platforms everywhere, allowing them to use any EMU they like. They celebrated this freedom by buying the very ugliest they could find:
They could do this because most platforms were built to the 76 cm level and not yet rebuilt to 96 cm, so there's actually not a lot of investment here. In the future the 96 cm level stations will need to be rebuilt, of course. This sucks for Regiobahn, of the white Talent at the start. They are part of the same network, and their fairly recent stations (opened in 1999) will all need to be rebuilt lower. They'll also need new trains, of course, but they're already planning to do that anyway since the line will be electrified (they'll get Stadler FLIRT from a batch order for them and other operators by the local authorities).
In light of all this mess, DB and the federal government have decided a comprehensive plan of action. In german, this plan is known as the "Bahnsteighöhenkonzept", because if there's one thing we can do, it's invent long words. The concept itself is actually a lot shorter than the word: Rebuild everything at 76 cm.
Needless to say that this plan has not found universal acclaim. Lots of regional networks have been rebuilt to 55 cm in the past twenty years, and together with the appropriate trains, they deliver a quality product. Changing everything to 76 cm will cost a lot of money (the plan does not include funding sources). It also decreases accessibility for double-deck trains - including the long-distance ones. It does make things nicer for customers of DB's ICE trains, but those are hardly the only or most frequent trains at most of the stations where they call, and they obviously ignore the vast majority of stations in Germany.
As of right now, all sixteen states have launched a formal protest against the plan, and they're planning a joint law initiative that would officially declare 55 and 76 cm to be equally preferred platform heights. At least the state of Baden-Württemberg has recently published a fairly detailed concept detailing which lines should get which height. The mess about dealing with the mess is probably going to continue.