Introducing the UK's first Tram-Train
The tram-train concept allows a railway vehicle to run as an on-street tram serving city centres and also as a commuter train running on existing local rail networks. Julian Turner gets the inside track from the University of Huddersfield’s David Crosbee on the pioneering, £60m Tram-Train project, which promises to transform the transport network in the city of Sheffield, UK.
David Crosbee is a senior research fellow at the University of Huddersfield's Institute of Railway Research. Previously, he was a dynamics and suspension engineer at Bombardier Transportation, before joining the Rail Technology Unit at Manchester Metropolitan University, where he specialised in railway vehicle dynamic modelling and wheel-rail interaction. In 2012, the Rail Technology Unit transferred to the University of Huddersfield to form a new group specialising in railway research.
Julian Turner: Please provide a brief overview of the Institute of Railway Research.
David Crosbee: The Institute of Railway Research (IRR) is led by Professor Simon Iwnicki and is part of the School of Computing and Engineering at the University of Huddersfield. We are specialists in wheel-rail interaction, and much of our work employs computer modelling to simulate the dynamic behaviour of railway vehicles and what occurs in the contact patch between the wheel and the rail.
The IRR's work is split between research and consultancy projects. Notable EU-funded programmes include DynoTRAIN, SUSTRAIL, SPECTRUM, D-RAIL and a new initiative called CAPACITY4RAIL. Consultancy wise, we have carried out work for most rail manufacturers, maintainers, operators and infrastructure owners.
The IRR recently supported the engineering firm ARUP during the design of the Gold Coast Rapid Transit System in Australia, where we carried out detailed analysis to check proposed alignments, and calculate estimations of rail wear, rolling contact fatigue (RCF) and derailment risks.
JT: Describe the Tram-Train concept and the specific advantages it offers compared with other urban transport solutions?
DC: A Tram-Train is a vehicle that can be operated in two transport modes: as a street tram serving city centres and also as a commuter train making use of the existing rail network. This dual operation provides greater flexibility, additional services and routes, and better connections for passengers.
If you have a railway line running through the city suburbs, then you could put in Tram-Train stops and provide local stopping service more easily, rather than having to build a whole new dedicated tram track.
The Tram-Train vehicles have to be designed to work with both types of infrastructure. They must work on the grooved rails within the street tram network and also be able to interact correctly with switch and crossing equipment as well as check rails on the mainline track. The wheel profile design was therefore important, since we had to ensure it could cope with street rails and heavy rail tracks.
JT: What was the impetus behind the Sheffield-Rotherham Tram-Train project and how is it being funded?
DC: The Sheffield-Rotherham Tram-Train project is a £60m pilot scheme and represents the UK's first trial of the Tram-Train concept. Its objective is to demonstrate the costs and benefits of operating a standard continental design of Tram-Train on the UK national rail network with the minimum of adaptation.
The benefits include the potential for lower infrastructure capital and maintenance costs compared to heavy rail service, and a level of passenger demand and satisfaction to be derived from using this new technology.
The consortium managing the project comprises the Department of Transport, Network Rail, Northern Rail, Sheffield Stagecoach Supertram and the South Yorkshire Passenger Transport Executive, with vehicles procured from transport technology manufacturer Vossloh.
JT: Has the Tram-Train concept already gained traction in Europe?
DC: It was initially developed in Karlsruhe in Germany, where they have linked a street tram network to the local passenger lines. In the UK, there are two implementations of the Tram-Train concept. The Tyne and Wear Metro was originally segregated, but now it runs a local service to Sunderland in mixed traffic on tracks shared with Network Rail.
The other one is Manchester Metrolink, which runs on grooved track in the town centre and then links to heavy rail lines adopted from previous railways. One of the key elements of the tram wheel design is that the flangeback has a step in it and we've incorporated that into our wheel design.
JT: How have computer modelling techniques informed the Tram-Train wheel design work?
DC: We used computer software to determine the contact conditions such as rolling radius difference, and contact stress and angle, between the wheel and the rail profiles. That information was then used to analyse the existing wheel profiles on the two systems with new and worn rails.
We carried out design iterations of the wheel profile to optimise the contact conditions; this gives us the best design compromise for successful operation on both Sheffield tram and Network Rail tracks.
Next, we determined the dynamic behaviour of the vehicle and conducted stability analysis to ensure that the design of the new profile doesn't impact on the risk of vehicle instability, known as 'hunting'. Curving analysis looked at something called T-gamma which is the energy dissipated within the contact patch, this was fed into our RCF and wear calculations. We incorporated both a rail wear and an RCF model into our code to predict rail damage rates throughout the route, which allowed us to make sure that the profile doesn't cause excessive wear or generate any levels of RCF.
We also conducted a whole route analysis to check for risk of derailment and to give us an idea of where areas of high wear might be on the rails.
JT: What have been the some of the main challenges associated with the project?
DC: The wheel design work was complicated by the very different rail head shapes of the two systems; the Sheffield Supertram network has a very flat rail head profile, while the worn Network Rail sections typically have a much smaller effective rail head shape. This necessitated compromise in the wheel and tread design, with significant simulation work being carried out to optimise the new wheel profile shape.
This allowed wheel-rail contact stress and wear rates to be minimised on both systems, while also maintaining safety against derailment.
JT: Can commuters expect to see tram-trains running in the UK in the near future?
DC: We've submitted our design to the Tram-Train project team for scrutiny and in time that will get submitted to the Rail Safety and Standards Board (RSSB) for approval, because it's a non-standard wheel profile, it has to be approved to make sure it is safe to run on Network Rail. Vossloh is also using the profile for optimising its suspension and once the wheel design has been approved by RSSB, the plan is that services will start at the beginning of 2016.
The Tram-Train will be running on Sheffield Supertram's system and on Network Rail. The services will run on Supertram infrastructure from Sheffield Cathedral out to a new station at Meadowhall South. There will be a spur off to an existing freight line running through Rotherham Central Station and on to a new station at Rotherham Parkgate.
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