In Northern Ireland, an average person does over 80% of their journeys by car. This is very high compared to other parts of the UK, where 63% of journeys are made by car, and in Ireland, where the figure is just over 50%. Belfast is also one of the most congested cities in the UK. These problems are because too many people are driving too often. Being too reliant on our cars to get around leads to many detrimental impacts. For example, we walk and cycle less, our air quality worsens, and the number of road traffic collisions increases. It is, therefore, a growing issue in public health with more and more cities looking for solutions to help reduce our reliance on cars. However, solutions to such a problem are not simple as there are many different groups involved in or affected by the transport system. If we are to find policies and programmes that help reduce car reliance long term, then these groups must work together to solve the problem. Our project aims to co-develop sustainable and scalable policies and programmes that reduce the reliance on cars in Belfast. Our project is organised into 3 workstreams: 1) understanding the multiple layers of the system that influence the reliance on cars in Belfast; 2) exploring the current evidence and knowledge of what has worked in other cities; 3) developing possible policies and programmes with key organisations to reduce car use. Our policies and programmes are aimed at citizens who use their car for work, school drop-off, leisure and other activities in Belfast. But other road users will also directly benefit from less cars on the road, through less air pollution and fewer road traffic collisions. The general population will also benefit from cleaner air, less noise, and potential positive impacts on climate change. Our research includes the following steps: 1. We will undertake a survey using a technique known as Network Analysis to help us understand the network of stakeholders involved in the development, implementation and evaluation of programmes and policies to reduce car dependency and how they might best work together. 2. We will undertake a survey with road users in Belfast to evaluate and rank the importance of influences on car dependency and on alternative travel modes, using a technique known as Discrete Choice Experiments. 3. To develop agreement among stakeholders about the nature, ordering and relationships between programmes and policies of different organisations to reduce car dependency, we will develop visual diagrams of the 'system' of the various aspects that affect car dependency, using a technique known as causal loop diagrams. 4. We will host workshops with local citizens to 'sense-check' promising intervention approaches and policies to explore and ensure the acceptability, utility, affordability, feasibility and sustainability of new initiatives. Possible policies and programmes may include, for example: improved public transport, with the introduction of a new rapid transit system; investment in urban greenways to increase walking and cycling journeys; expanding the car-free areas of the city centre; extension of 'park and ride' and 'park and stride' facilities at the edge of the city. Our work will have the following outputs: 1. Identification of stakeholders influencing car dependency in Belfast and their relationships. 2. A review of the evidence for actions to reduce car dependency, leading to identification of possible new interventions and policies to be considered by stakeholders. 3. A map identifying ongoing and planned policies and interventions and their potential interplay. 4. A suite of potential co-ordinated policies and interventions 'tested' (in terms of acceptability and feasibility) with road users and local citizens. 5. A consensual understanding of the evidence provided and implications for reducing car dependency in Belfast. 6. A roadmap for multi-sectoral action to reduce car dependency in Belfast.