The RM transit youtube channel has an interesting video called The Modern Tram Has Gone Off the Rails. It basically describes a situation where tramway lines were built with the kind of heavy infrastructure (underground stations) where you would typically build a subway, an S-bahn, or just a regional train.
The video seems to explain this by some fashion phenomenon, i.e. that having a tramway is cool. That’s probably a factor, but I feel this might be a terminology problem, i.e. that transit gets built that way because of the way deciders think about it, and this is heavily influenced by the terminology, how things are named. If you can only describe a system as light rail, well, you build a light rail system.
In Europe, nobody talks about “light” and “heavy” rail. The french call light rail métro léger, which comes with its own semantic luggage – Paris has a métro (subway), other towns a cheap copy. Even before Karlsruhe, trains that carried lower volumes of passengers, with short trains, frequent stops and maybe ran a bit on the street were a common thing. In Zürich the Forchbahn, is a typical example of this, so is the Bremgarten-Dietikon-Bahn. These lines are old, the Forchbahn was basically rebranded as an S-Bahn (S18).
The definition for light rail from the American Public Transportation Association is the following:
…a mode of transit service (also called streetcar, tramway, or trolley) operating passenger rail cars singly (or in short, usually two-car or three-car, trains) on fixed rails in the right-of-way that is often separated from other traffic for part or much of the way. Light rail vehicles are typically driven electrically with power being drawn from an overhead electric line via a trolley [pole] or a pantograph; driven by an operator onboard the vehicle; and may have either high platform loading or low-level boarding using steps.
So it’s not train that is light, although it is a bit – most US tracks allow for 30 to 35 tons per axle, where in Europe the norm is 22.5. A CityLink tram typically weights 66 tons for 8 axles, so below 10 tons per axle. So what is supposed to be light is the general cost of deploying these trains. Per unit, tramways are not that cheaper than local trains (a Citylink is 8M€, a Flirt is around 10) , and per passenger, they are more expensive. The real problem is, this definition covers a good part of the rail traffic in Switzerland, tramways, of course, but also things people would consider just local trains, leaving me to wonder what exactly is cheaper when building a light railway as opposed to a normal one?
If you ever go to Chur (which I recommend), you will notice that there are tracks both inside the station and in front of it. Inside the station you have both the SBB/CFF/FFS tracks in standard gauge, and the RhB tracks in metric gauge. The tracks in front of the station are also meter gauge, and are also served by RhB trains, that go to Arosa. Service on these tracks is typically done with short trains, that run in the streets of Chur. If you look at open railway-map you will notice that these tracks on the street are not marked “light-railway”, probably because they connect to the same tracks inside the station, which are not
On the rolling stock-side, various railways have for many years experimented with lightweight vehicles on train tracks, in France the “Michelines”, in Germany the “Schienenbus” (Railbus), in Switzerland the Red Arrow. Stadler’s GWT is a typical example of a modern light railway vehicle, one of the lines it ran on first was the Biel–Täuffelen–Ins line, with metric gauge, frequent stops, rarely more than 2 km apart, and a part of the way runs on the street.
If you look at the M1 line in Lausanne, it uses Bem 4/6 EMUs, the nearly identical Bem 550 was used by the SBB on a local line between Geneva and Bellegarde (France). Same gauge, similar vehicles, one is light-rail, the other is not. The Bem 550 were replaced by FLIRTs and there are projects to have trains that continue out of the M1 tracks unto the regular SBB network.
The one domain where “light-railway” actually means something is legal. In France, if you build a tramway or a métro-léger, you are not stepping on SNCF’s toes. I suspect there is something similar in the US: if you build a light-railway, you don’t have to worry about FRA regulations. Being disconnected and incompatible with the regular train system is a feature, not a bug.
For me, the problem is that this classification should not matter, one should plan in terms of needs, i.e. moving people using public transport from A to B, and select the appropriate means, which above a certain threshold means a thing that runs on rails. The problem with the systems described in the movie is that they are light rail, that is, a mix of various systems that fall into this category.
What I find interesting is that Stadler, which is the rising star in light and regional rail, comes from an environnement where this distinction does not exist, and whose products often straddled the lines between the categories…