Diesel trams: a new way forward?
By Charles King – Modern Railways March 2007
A comparrison of Diesel-Hybrid and Electric only trams
# of Vehicles 10 18
Power rating 600kw 600kw
# motors 4 4
Accelerattion 1.1 ms2 1.1 ms2
Max. Speed 100 kph 100 kph
Weight 85.2 T 82.5 T
Seating Cap. 90 90
Standing Cap. 139 139
Boarding Ht. 360mm 360mm
Length 37.48m 37.48mm
Width 2.65m 2.65m
Min. radius 22m 22m
- Diesel TramTrain at a rural station
Twenty-eight three-car vehicles were ordered for the project, 18 electric-only and 10 diesel hybrids. Built by Alstom, they are part of the Regio Citadis family. Both versions are visually very similar, and share many features for ease of maintenance. Crucially, performance is the same for both electric-only and diesel-hybrid vehicles – acceleration from start is 1.1ms the vehicles is given in the table above.
Transferability / applicability to UK
As stated above, conditions for tram-train have to be right, and given the small number of tram systems in the UK, let alone other complexities in the development of a scheme, it is clear that imitating the Karlsruhe model here is a harder task. The Sunderland extension of the Tyne & Wear Metro used some tram-train principles but employed the existing electric Metro vehicles, and areas including Greater Manchester and Teesside have been looking at the use of tram-trains. It would seem that in the UK context, diesel tram technology could help broaden tramtrain’s appeal, especially in increasing the affordability of light rail schemes, and where funding has been withdrawn owing to cost overruns as in the Leeds Supertram project. Potentially they combine the speed of a railway and the accessibility of a tramway, at a much lower capital cost than electric trams.
Joining up urban centres
First, taking advantage of a tram’s ability to penetrate the urban centre, a tramway spur from the mainline to such ‘honey pot’ sites offers the opportunity to go right to where the customers want to go and encourage modal shift with seamless journeys. If Karlsruhe has shown that through journeys work with electric vehicles, then diesel trams prove that a potential station crucially need not be sited on an electrified Network Rail line – thus opening up the entire British railway network – nor would the tramway itself require electrification. Blackpool illustrates the potential: diesel trams offer the prospect of linking up the South Fylde line with the tramway, thereby opening up many new journey opportunities and contributing to the area’s regeneration. As no electrification would be necessary, major new infrastructure would be confined to connecting the two networks and restoring some of the double track on the railway section.
The attraction of diesel trams does not merely lie in their ability to operate as urban street vehicles. With regard to rolling stock operation, in a climate where everything must be increasingly accountable, does it always make sense to run conventional trains on rural routes or a small shuttle service? Running a diesel tram over the St Erth – St Ives or Marks Tey – Sudbury branch, for example, could result in lower infrastructure operating and maintenance costs, as well as freeing up the conventional DMU for use elsewhere. A diesel tram-style service could also allow extra stops to be served, as suggested for the Tees Valley for instance. If more capacity is needed, several units can be coupled together (up to four can run as a ‘train’ in Kassel). Of course, the ultimate is full conversion of the line to tramway standards with simplification or even removal of signalling – driving on ‘line of sight’ – and again lowering track maintenance costs. Retaining the option of through running onto the mainline would open up many more possibilities, and also allow access to existing maintenance facilities elsewhere on the network if required.
There are signs that the industry is looking towards an approach where operational and maintenance standards on a line are more closely dictated by its function and the type of traffic it sustains. We must be ready to accommodate this shift in focus if it secures the longer-term future of more lightly used lines and ensures they remain fit for purpose. Community railways are a prime example of this: if a certain route with a low line speed only sees a few passenger trains a day operated by Pacers and no freight, why could this service not be provided by a diesel tram with its attendant cost savings and, from the passengers’ perspective, a more comfortable journey experience?
Diesel trams will not provide the answer in all cases, but they have clearly helped to provide new impetus to the tram-train concept as well as demonstrating their value as rail vehicles in their own right. At a time when the train-infrastructure interface comes under closer scrutiny, considerably lighter tram-type vehicles could contribute to a ‘virtuous maintenance circle’, and Network Rail’s vision for a more reliable railway. In the effort to maintain and grow rail’s attractiveness through ‘joined-up journeys’, and to ensure that each line is used as appropriately as possible, light rail technologies are likely to play an increasingly important role. Diesel trams are well placed to form part of that mix.
2-Diesel TramTrains in multiple unit operation
Following a year’s internship in Germany with DB (German Rail) and a transport planning consultancy, Charles King joined the Transportation Division of Faber Maunsell as a rail transport planner. Last year, on behalf of ACoRP, he organised the tram-train study visit to Switzerland and Germany referred to in this article.
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