PhD Defence Camill Harter

In his dissertation, Vulnerability Through Vertical Collaboration in Transportation: A Complex Networks Approach, ERIM’s Camill Harter showed that vulnerability in collaborative transport networks is strongly influenced by the market structure of carriers; systems with mainly similar-sized carriers are robust to targeted disruption, whereas the total magnitude of potential failure is very large; systems with a few dominating players have a lower magnitude of failure but are highly susceptible to targeted disruption; moreover, there is an optimal level of collaboration where the increasing risk of disruption cascades outweighs the decreasing marginal added benefits of additional collaboration.

Camill defended his dissertation in the Senate Hall at Erasmus University Rotterdam (EUR) on Friday, 10 March 2023. His supervisors were Prof. dr. Rob Zuidwijk (RSM) and Prof. dr. Otto Koppius (RSM). Other members of the Doctoral Committee were Prof. dr. Albert Veenstra (RSM), Prof. dr. Marie Schmidt (Universität Würzburg), Prof. dr. Alexander Verbraeck (TU Delft), Prof. dr. Lóránt Tavasszy (TU Delft), Prof. dr. Violeta Roso (Chalmers), and Prof. dr. Niels Agatz (RSM).

This research addresses vulnerabilities that emerge from vertical collaboration in complex transportation networks with multiple carriers and transport modes and provides decision support tools for policy making in the field of collaborative transport. Vertical collaboration in our context describes the integration of service networks of different carriers and transport modes, and comes with many benefits such as efficiency, utilization of infrastructure & carbon footprint reduction. However, a higher level of collaboration creates new dependencies, for instance induced by the need for coordination, information exchange, and interconnected information systems, which can ultimately turn into disruption threats. While the benefits of vertical collaboration are extensively covered in existing research, knowledge on the concomitant vulnerabilities has been rather limited. We developed a novel multi-layer network model to capture both the physical and collaborative aspects of transportation networks with vertical collaboration in an integrated fashion and analysed it with a combination of well-known metrics from network science and new methods developed ourselves. We show that vulnerability is strongly influenced by the market structure of carriers. Systems with mainly similar-sized carriers are robust to targeted disruption, whereas the total magnitude of potential failure is very large. Systems with a few dominating carriers have a lower magnitude of failure but are highly susceptible to targeted disruption. Moreover, there is an optimal level of collaboration where the increasing risk of disruption cascades outweighs the decreasing marginal added benefits of additional collaboration.

View photos of Camill's PhD Defence

Photos: Chris Gorzeman / Capital Images