Boundaries of Tram Operation Extended Beyond the Catenary

Alstom’s STEEM system, under testing in Paris, will allow vehicles to run between stops without a catenary.

In January, Bombardier announced the development of a new traction system called Primove that will allow trams to receive power wirelessly by communicating with circuits buried underneath the track. The implementation of this technology would allow streetcars to travel through cities at moderate speeds without requiring the construction of overhead catenaries, whose wires are often seen as the major downside of modern electric rail transit. With its new STEEM system, competitor Alstom may be able to offer the same advantages through battery power storage — at a far lower cost.

Primove has a major advantage — the fact that its power devices are buried — over a similar Alstom system currently being used in the city of Bordeaux, which relies on an exposed third rail that is only activated as a tram passes over it. This means that Primove could theoretically be used in colder, wetter climes, places where the Alstom third rail system is likely to run into trouble. But both of these technologies are significantly more expensive to build and implement than traditional catenary, meaning that they’re only likely to be used in the most historically-sensitive areas where overhead wires are seen as too distracting.

If implemented, Alstom’s new STEEM system*, on the other hand, will require less catenary wire and no underground construction; it simply requires the upgrading of existing tram vehicles. Trains will be equipped with large batteries connected to their motors that will be charged each time the vehicle brakes, much like the way a Toyota Prius hybrid refills its battery. In addition, the trams will be able to benefit from charging during 20-second station dwell times, where trains will benefit from a catenary; theoretically, the system wouldn’t require the use of the catenary between stations.

Alstom’s technology is a major advance, and it could cut down investment costs in light rail projects significantly in areas where stations are close enough to ensure that trains can move between them without running out of power. In short, it means that transit agencies could install tracks without the relatively expensive overhead catenaries between stations, putting them only above stops, where they’ll serve as recharging units alone. This is a bigger advance than Bombardier’s more exciting announcement earlier this year because it will result in less expensive construction and operations costs.

Though the city of Nice in the south of France already has a first generation version of this system, allowing trains to run without catenaries in the city’s central square, STEEM allows for quick recharging and use throughout a vehicle’s journey, something not previously possible. The system will undergo testing on two sections of Paris’ T3 light rail line, at first using one vehicle that will simply retract its pantograph in the testing sections and operate autonomously even as the other trains on the line continue to use the catenary there.

Alstom’s technology is not yet advanced yet to work on fast-moving American light rail systems, which typically have station stops up to a mile apart, likely too far for its battery capacity to handle. Whether the system can handle the incredible wastefulness of air conditioning — something not present in Paris — is a different question. But it could be particularly useful for streetcar networks, such as the one planned in Washington, D.C., where a congressional ban on overhead wires is still in effect — something that could likely be circumvented if the wires were only present at stations. In cities like Portland where light rail stations downtown are just blocks apart, the technology could mean the ability to get rid of overhead wires in central sections of the network.

* Système de tramway à efficacité energétique maximisée (maximized energy efficiency tramway system)