Towards a sustainable integrated transport system architecture: light rail development

In the last two decades in Europe, the electric tram system has been the preferred choice of public transport to influence modal shift. However, in the UK, such schemes have proved difficult to implement due to their perceived high cost, long approval and implementation times, strong public opposition, and the perceived unsightliness and unacceptability of their overhead power supply in sensitive or historical city centres. This research addresses these problems in the light rail industry, firstly by analysing the perceived barriers to implementing light rail using a Soft Systems Methodology, and secondly by exploring the technical issues of alternative forms of on-board power supply, such as batteries. In particular, the research looks at the feasibility of retro-fitting on-board energy storage to an existing fleet of vehicles, a solution which has not been extensively explored in the literature.

The research approach adopted was a mix-method case study design. The problems in light rail, and indeed in transport generally, are what social scientists have termed "wicked problems," that is, problems arising from social or cultural issues or concerns that are difficult to explain and inherently impossible to solve using standard traditional techniques. Based upon the need to address these wicked problems in the light rail industry, a soft-systems model (SSM) was developed and was incorporated into the investigation and knowledge acquisition in the light rail industry. The SSM led into the hard-systems methodology which was used to address the technical problems of on-board energy storage.

The SSM phase of the work entailed obtaining information and views from a wide selection of stakeholders in the light rail industry, to identify and then analyse what are the main barriers to the further developments of light rail systems in the UK. Preliminary discussions were used to develop an open-ended questionnaire which was used to guide questions during a series of semi-structured interviews with industry stakeholders. Having identified these barriers to adoption, the research then turns them into a technical problem, a problem that is amenable to management through professional intervention, by developing a Rich Picture of the interactions between stakeholders and proposing some recommendations for overcoming the barriers.

The SSM led into the hard-systems methodology, which involved the development of a technical questionnaire to obtain quantitative data from manufacturers and operators. Subject matter experts were sought to validate data collected from the energy storage manufacturers.

In this research, alternative energy storage technologies for mass transit transportation are explored in-depth. Five types of different energy storage are studied—flow battery, supercapacitor, lithium-ion battery, lithium supercapacitor, and lead-acid battery. The results showed that the lithium-ion battery is the most suitable choice for catenary-free adoption. The feasibility study used a real city in the East Midlands region of England as a test-bed. In the case study, the battery-powered section is 1.6 km, which is 6.7% of the whole line. From the energy consumption data analysis, it is confirmed that there is sufficient space to house enough batteries to supply the power requirements even in the worst-case scenario. This confirms that retrofitting energy storage is possible on an existing Bombardier Incentro and Alstom Citadis vehicles for a catenary-free option. The study showed that the optimum design is catenaryfree for up to 20% of the total line in the absence of other constraints. This thesis represents a contribution to knowledge in the field of energy management. The characteristic is generalised and can be applied to other mass transit, such as heavy rail, bus, coach or other city transportation.

The soft and hard data collected contributed to the results in the Socio-Technical Systems analysis. In practice, there were some overlap between SSM and HSM. The Socio-Technical Systems analysis suggested, as further work, the development of a feature tool with important metrics of interest identified – an onboard energy storage and cost calculator. The feature tool could then be used to analyse power requirements for light rail vehicles with other characteristics in other cases, and for mass transit modes more generally in other cities.