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Unplanned urban passenger rail disruption – new methods and perspectives on bus bridging

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posted on 23.02.2017, 02:15 by Pender, Brendan Michael
In a time of increasing road congestion, passenger rail networks provide superior performance to commuters in terms of capacity and speed compared with other road-based transit modes. Although their technical complexity greatly assists in delivering these improved service levels, it also makes them vulnerable when unplanned disruptions occur. Such unexpected occurrences can be due to infrastructure malfunctions, accidents and extreme weather conditions and result in trains being delayed or not operating at all. These incidents can often result in the rapid degradation of existing service levels given that the options for alternative internal solutions are limited. This is unlike the road network, where when one link fails, traffic can be diverted to neighbouring roads. Unfortunately passenger railway networks are not as resilient and often a common solution to addressing disrupted commuters’ travel needs is to provide alternative transportation modes such as buses. This thesis explores unplanned service disruptions to passenger rail networks and develops new proactive planning approaches to better respond to these events. Whilst planned service disruptions similarly result in reduced service levels, it is the unexpected nature of unplanned nature of unplanned disruptions that makes responses so critical. The focus is a practice known as bus bridging. This involves establishing short-term bus routes to restore connectivity between railway stations that have experienced some form of intervening service disruption. Research on the effects of transit service disruption is limited. The focus of previous research has related to internal solutions to rail disruptions, that is, train timetables, rolling stock or crew adjustments. Although limited research has explored the role of bus bridging during unplanned service disruptions, its focus has been on reactive measures assuming available and adequate resources. A key knowledge gap in this regard relates to proactive planning methodologies to aid bus bridging solutions and in particular the role that track crossovers (locations to turn trains) and dedicated bus reserves (both location and size) plays in this respect. An international survey of current practice conducted as part of this thesis discovered that 87% of 92 passenger rail transit agencies used bus bridging as a solution to unplanned network disruptions, while 92% of these agencies made use of spare buses to provide bus bridging services when required. This survey also highlighted the importance of parallel public transport networks in managing unplanned passenger rail disruptions, although parallel systems could rarely meet demand. Some 80% of participating agencies noted the importance of rail crossovers in managing unplanned service disruptions. The results of this thesis suggested that only a few unplanned passenger rail disruptions annually would make providing track crossovers financially viable on the basis of savings in bus bridging service costs. Research found that locating track crossovers as close as possible to areas of major disruption provided the most benefits for commuters and rail agencies. This thesis demonstrated that strategically locating bus reserves according to criteria such as disruption likelihood provides the opportunity to better cater for the disrupted demand for rail travel. New methodologies presented highlight how ideal depot locations change in relation to criteria including: travel time to bus bridging termini, likelihood of an unplanned service disruption and commuter volumes affected. The ideal bus reserve location may not be fixed and could vary by time of day and disruption demand. Subsequently, the concept of satellite bus depots and mobile bus reserves was introduced, neither of which require permanent fixed depot facilities. Introducing randomness in some of the aforementioned variables highlighted the possibility of multiple depot locations to service the one group of rail lines. Not only were the ideal locations for such bus reserves still determined but secondary and tertiary locations were also identified. Exploring the feasibility of dedicated bus reserves purely for bus bridging purposes, with the aid of a proposed analytical approach, demonstrated that for approximately three quarters of the rail corridors analysed, dedicated bus reserves were economically viable with respect to reducing disrupted commuters’ waiting time for bus bridging commencement. This thesis provides an important contribution to knowledge in the field of unplanned passenger rail disruption management. Although these incidents are unexpected in nature, it is possible to effectively plan for the unplanned. Proactive planning methodologies are increasingly applied in related fields such as emergency service management; however, in passenger railways the limited focus has been on reactive approaches. Whilst there are limitations in this research (documented in the Conclusions chapter), it is anticipated that research work completed as part of this thesis will assist researchers and industry practitioners as they try to further develop recovery approaches to unplanned disruptions and attempt to balance the costs associated with pre-emptive resource allocation and the economic costs or disbenefits to commuters when such events occur. Although not integral to this thesis’s key outcomes, this research also highlights the importance of social media in unplanned service disruption management. Given the ability of social media to inform commuters before they travel by train, such a proactive approach could ideally complement the proactive response techniques that form the basis of this thesis.


Campus location


Principal supervisor

Graham Currie

Year of Award


Department, School or Centre

Civil Engineering


Doctor of Philosophy

Degree Type



Faculty of Engineering