The Anonymous Widower

The Third-Rail Tram-Train

I’ve never seen anybody propose a third-rail powered tram-train, but that is probably because everybody has assumed quite rightly, that you couldn’t power a tram by using third-rail electrification. It’s just too dangerous!

In February 2016 I wrote Brummies Go For Battery Trams and it is now ienvisaged that Midland Metro‘s trams will be running services under battery power in 2019.

As battery power is used for trams in several places around Europe and the world and is becoming a proven technology, is there any reason why a battery tram-train, can’t be powered by third-rail electrification, when running as a train?

The Class 399 Tram-Train

The Class 399 tram-train is under test in Sheffield, to prove that it can run passenger services in the UK.

These tram-trains can handle either 25 KVAC or 750 VDC from overhead wiring.

Stadler, whose Valemcia factory built the Class 399 tram-trains, will also be building trains for Merseyrail’s network, which runs using 750 VDC third-rail electrification.

Would it be reasonable to assume, that Stadler will be able to design an appropriate pick-up shoe for the Class 399 tram-train, so that it can run on a 750 VDC third-rail network?


A battery system would also be needed, but I believe that this will be generally offered by all tram and tram-train manufacturers, as trams and tram-trains will be running increasingly in sensitive heritage area.

Charging The Batteries

Batteries would normally be charged, when the tram-train is running on an electrified line, under power from the third-rail system.

The MetroCentro in Seville, works without catenary andhas a fast charging system  at the two end stops.

There is no reason to believe that a Class 399 tram-train with batteries, couldn’t work with a fast charging station like a Railbaar.

Would A Third-Rail Tram-Train Have A Pantograph?

This would be a matter for the operator.

But there is one UK tram network; the London Tramlink in Croydon, which is surrounded by an extensive third-rail electrified network.

The ability to run on both types of 750 VDC systems might be an asset and enable new services to be created without any extra electrification, by using a small amount of battery power to change from one system to another.

Range On Third-Rail Power

The range of a Class 399 tram-train running on third-rail power, would be more limited by the train-tram’s speed of 100 kph and interaction with other services, rather than any electrification issues.

The range will probably be the same as the German cousins of the Class 399 tram-trains on the Karlsruhe Stadtbahn. These trams run on both 750 VDC and 15 KVAC, to places up to fifty kilometres from the Centre of Karlsruhe.

As a simple example, a third-rail tram-train running on the London Tramlink, could certainly use third-rail lines to access Gatwick Airport.

Range On Battery Power

In Out Of The Mouths Of Brummies, which describes an interview with those involved in the Midland Metro battery train project, I published this quote about battery trams.

Since then there has been lots of work and we’re now comfortable that battery technology has advanced sufficiently for it to be viable.

Under test conditions with plain straight track a tram could travel 20 km catenary-free. In practice, this would be rather less for a fully laden tram ascending the 9% gradient on Penfold Street. The longest catenary-free run we’ve envisaged is around 2 km, and we’re comfortable we can achieve that.

I think until Birmingham proves otherwise, 2 km. would be a sensible range for a tram or tram-train running on a full battery.

Compatibility Issues With Other Rail Vehicles And Platforms

This to me is a matter of design, but after the Sheffield tram-train trial and the analysis of platform solutions in Europe, I suspect that we’ll come up with a solution that works.

I think it is true to say, that many of our trains are badly matched to the platforms, but as this picture of a Class 378 train on the London Overground shows, the gap is becoming easier to mind.

I think too, we have an advantage over Europe, in that our loading gauge is smaller and our trains are closer in size to a modern tram or tram-train.

We are also good at innovative access solutions, as this picture from Canonbury station shows.

We may have a problem with using double-deck trains, but I believe that good design can minimise the problems of good access to both trains and tram-trains at the same platform.


The applications will be limited by battery range and by the gradients of the line.

In Southampton – A City Built For Cars, I describe how if they built their proposed Solent Metro around third-rail tram-train technology, they could transform the city.

In Could Beckenham Junction To Birkbeck Be Run Using Third-Rail Tram-Trains?, I show how third-rail tram train-technology , could be used to create more capacity at Beckenham Junction station.

In Could Third-Rail Tram-Trains Be Used To Increase Services In South London?, I show how third-rail tram-train technology, could be used to expand the London Tramlink.

In Could Third-Rail Tram-Trains Work The Epsom Downs Branch?, I show how third-rail tram-train technology, could serve the Royal Marsden Hospital.


Technically, I feel that a Class 399 tram-train capable of running on third-rail electrified lines is possible.

But it would have to run on battery power or 750 VDC overhead, when running as a tram.



April 14, 2017 - Posted by | Travel | , , , ,

1 Comment »

  1. […] But as the line is electrified with the standard 750 VDC third-rail system, it is one of those places, could it be served by a third-rail tram-train, as I proposed in The Third-Rail Tram-Train? […]

    Pingback by Could Third-Rail Tram-Trains Work The Epsom Downs Branch? « The Anonymous Widower | April 16, 2017 | Reply

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