Group model building for developing systems-oriented solutions to reduce car dependency in Belfast, United Kingdom

The continued prevalence of car dependency is a concern worldwide due to known negative health, social, economic, and environmental impacts. Belfast is a city in the United Kingdom with high levels of car dependency and car use. The most successful interventions to reduce the complex problem of car dependency combine a range of approaches, but how the influencing factors work together and interact to successfully achieve a change in car dependency is poorly understood. This study aimed to better understand the factors that influence the high levels of car dependency in the Belfast Metropolitan Area. We worked with 17 stakeholders to co-design a causal loop diagram to understand the complex system of car dependency in the city. The causal loop diagram reflects a shared understanding of car dependency and highlights the various mechanisms that are important for reducing car dependency. Twenty-three factors under the four themes of policy, infrastructure, economics, and social norms were identified and four key feedback loops between these themes are discussed. It is shown how individual behaviour in relation to travel mode choice is influenced by system-wide factors that, in the Belfast context, make car use the easiest and most convenient choice for the majority.