Question for UK rail fans - about tram-trains

[Slugger Onions]

Hi to all UK rail boffins.

I'm a New Zealander with an interest in PT trying to get some information on tram-trains. It's not easy for me to come by information so I thought I'd see if there were informed people on this forum. I know the UK doesn't actually have any tram-train operations and quite probably won't, but my fluency in the German and French languages are well below conversational level.

From what I've been able to gather tram-trains are built to mainline safety standards and probably because of that, weigh considerably more than conventional trams and units for light-rail EMU's.

So why are they regarded as light rail?

I always though light rail is light rail because it's not sharing the mainline corridors with any heavy rail and don't need to be built to mainline safety standards.

It seems inferred (naturally I suppose) that tram-trains are trams that can run the mainline. But the more I research I can't help but think of tram-trains as the opposite; as really heavy-rail railcars that can run on (strengthened) street-embedded tram infrastructure. And of course they have the form/body of trams.

Or are my perceptions of what light and heavy rail are, simply askew?

 

[WatcherZero]

Ok a few answers.
1. There is a tram-train trial in the late planning stages, its a concept that is being heavily embraced by Northern metros as a way of boosting frequency and capacity on their suburban lines with a lower investment than heavy rail and with different routing possibilities utilising tram networks they can serve the city streets rather tham just a city centre station.

2. They actually weigh about half way between a LRV and a Train, their direct parent is a tram and most of their equipment comes from it but higher crashworthiness, support for mainline signalling, dual power supply voltages (or diesel-electric) or pickups (shoes/overhead), higher speed, etc... are added.

3. Light rail refers to the infrastructure rather than the weight of the vehicles though they are usually lighter. Its simpler signalling, weaker and cheaper bridges/viaducts (since the vehicles have a lower top speed), less deep foundations for track, less extensive facilities at stops (e.g. no toilets) etc... The capacity (length) of the vehicles is also usually smaller 'lighter' than a full metro like an Underground or high capacity people mover. Some light rail systems are sometimes refered to as a 'pre-metro' system, that is initial infrastructure and vehicles that can be converted to a full metro several decades down the line for example by burying the tracks beneath the street or adding longer/more frequent services.

 

[Slugger Onions]

Ok a few answers.
1. There is a tram-train trial in the late planning stages, its a concept that is being heavily embraced by Northern metros as a way of boosting frequency and capacity on their suburban lines with a lower investment than heavy rail and with different routing possibilities utilising tram networks they can serve the city streets rather tham just a city centre station.

2. They actually weigh about half way between a LRV and a Train, their direct parent is a tram and most of their equipment comes from it but higher crashworthiness, support for mainline signalling, dual power supply voltages (or diesel-electric) or pickups (shoes/overhead), higher speed, etc... are added.

3. Light rail refers to the infrastructure rather than the weight of the vehicles though they are usually lighter. Its simpler signalling, weaker and cheaper bridges/viaducts (since the vehicles have a lower top speed), less deep foundations for track, less extensive facilities at stops (e.g. no toilets) etc... The capacity (length) of the vehicles is also usually smaller 'lighter' than a full metro like an Underground or high capacity people mover. Some light rail systems are sometimes refered to as a 'pre-metro' system, that is initial infrastructure and vehicles that can be converted to a full metro several decades down the line for example by burying the tracks beneath the street or adding longer/more frequent services.

Thanks for the speedy answer.

As regards point 2. When you look at the weights of the tram-trains currently offered by manufacturers;
Alstom RegioCitadis: 59.8t (and 63.4t with Diesel generator)
Alstom Citadis Dualis: 77t (!)
Bombadier Flexity Link: 51.8t
Bombadier Flexity swift for Karlsruhe: ~62t
Siemens RegioSprinter: 49.2t
Siemens Avanto: 59.7t
Vossloh S4100: 55.5t
Vossloh Citylink: 57.5t

Or the older rolling stock for the Karlsruhe network;
GT 8-100C/2S: 58.6t
GT 8-100D/2S-M: 59 t

These are in the same weight range as a 2-car EMU on the lighter end of the scale as you'd expect to find in German S-bahn's or the single-decked commuter units used in France.


And as they run on the mainline I'd expect them to have the same sort of electric drive motors and braking that an EMU or railcar would have.
That's why I'm suspecting that most of what they have in common with trams is purely cosmetic.



With point 3. It appears that my definition of light rail was a bit off, and that it goes beyond mainline safety standards (although surely signals would be an aspect of that).

But as they conform to signals, line speeds and the infrastructure of heavy rail; I still can't understand why they're regarded as light rail (other than their lower passenger capacity).

 

[142094]

It depends on the definition of 'tram', 'tram-train', 'light rail' and 'heavy rail'. The first three are sometimes used interchangeably, which in my opinion is incorrect. A tram runs on street level but may also use grade-separated track, such as Manchester Metrolink, but doesn't share track with other rail services. Tram-trains would be able to use both street-level and grade-separated routes and also share some lines with heavy rail - e.g. there were plans for the Penistone line and Harrogate loop to be converted to tram-train, but in theory you could still run a normal heavy rail service on the line (just depends on platforms).

Light rail is totally grade-separated, does not run on street level. However, it may also share tracks with heavy rail services - Karlsruhe in Germany was the first to implement this and we now have the Tyne and Wear Metro running on Network Rail tracks between Pelaw and Sunderland in the UK.

Light rail doesn't necessarily have to mean lighter infrastructure or signalling - the Tyne and Wear Metro is signaled much in the same way as a normal railway and the infrastructure is just about the same as you'd get anywhere else - indeed British Rail used to run freight on parts of the line in early years. Construction of the stations and tunnels was slightly different which would make some heavy rail operation difficult.

 

[WatcherZero]

T&W was apart from the tunnels converted from existing rail lines though, the 3rd rail electrification which had been there for 70 years was lifted when it was converted to Diesel then put back a decade later when it became the Metro. They ran the freight through a process of temporary possesion though didnt they? When a freight train was on the tracks the Metro cars in that section wernt allowed to move.

Your right though the terms can be quite fluid as systems have a few aspects which would fall into other categorisations and even Heavy Rail sometimes shares roadspace at crossings or on freight lines where it can run down the middle of a road.

 

[Slugger Onions]

It depends on the definition of 'tram', 'tram-train', 'light rail' and 'heavy rail'. The first three are sometimes used interchangeably, which in my opinion is incorrect. A tram runs on street level but may also use grade-separated track, such as Manchester Metrolink, but doesn't share track with other rail services. Tram-trains would be able to use both street-level and grade-separated routes and also share some lines with heavy rail - e.g. there were plans for the Penistone line and Harrogate loop to be converted to tram-train, but in theory you could still run a normal heavy rail service on the line (just depends on platforms).

Light rail is totally grade-separated, does not run on street level. However, it may also share tracks with heavy rail services - Karlsruhe in Germany was the first to implement this and we now have the Tyne and Wear Metro running on Network Rail tracks between Pelaw and Sunderland in the UK.

Light rail doesn't necessarily have to mean lighter infrastructure or signalling - the Tyne and Wear Metro is signaled much in the same way as a normal railway and the infrastructure is just about the same as you'd get anywhere else - indeed British Rail used to run freight on parts of the line in early years. Construction of the stations and tunnels was slightly different which would make some heavy rail operation difficult.

My understanding is as follows:

Trams are trams or what the Germans call Straßenbahn. They're a rail vehicle that runs down the street on embedded grooved rails doing something similar to what a bus does (but with greater capacity).

Light rail is completely grade separated dedicated city and suburban rail (that's not a metro although is sometimes called a "pre-metro" with the intention of later upgrading to a full-on metro). It doesn't need to conform to mainline standards. The Germans call it Stadtbahn.

The lines between the two and even metros are often blurred. In most countries a Light rail/stadtbahn is legally recognised as a tramway and subject to the same regulations. Most light rail vehicles are capable of on-street running through regular grooved tram-tracks provided the wheel tires are of a suitable profile (and vice versa with trams). In many places there are systems with elements of both such as regional tramways and light rail that does have tram-operation (despite the higher-floored carriages).
And in Frankfurt, Essen and Stuttgart (and I guess Tyneside) they've even got an U-Stadtbahn where the light rail operation is mixed with a metro operation under the CBD. Frankfurt's is even officially called an U-Bahn (metro). And yet in Frankfurt and Essen they also have sections of on-street tram operation (I don't know about Stuttgart).

It all becomes a bit confusing.

But with tram-trains it seems a bit clearer; they're supposedly trams that can operate on mainline heavy rail infrastructure.
Except the more I look at them the more I wonder if they're really heavy rail in the shape of a tram that can do what a tram does (on upgraded tram tracks).

 

[ChrisCooper]

To throw another one into the mix, a "Light Rail Order" is what heritage lines operate under, although they use heavy rail stock, signalling, and infrastructure. In this context, especially when taking into acount the historical use of the orders (short private lines linking up with the mainlines), "light" refers more to light use or light traffic. Oviously though that's the total opposite to the more modern "light rail" where traffic is very heavy, often far more heavy than "heavy rail" (many lines which only see 1 or 2 tph, compared to 6, 12 or even more TPH on "light rail").