System Dynamics Evaluation of Traffic Safety Policy : A Feasibility Study

System dynamics (SD) is a method for learning about complex systems and it includes a range of tools such as causal loop diagrams and computer simulation. SD has been used to facilitate the analysis of complex physical and social systems, e.g. water resources, climate change and industrial accidents. One of the key reasons for its growing popularity is that SD allows policy “experimentation” and facilitates discussion of “what-if” scenarios. Due to the complexity of traffic policies, SD has been used to facilitate traffic policy analysis. However, there is a lack of application of SD in traffic safety policy, which tends to focus on micro level issues, e.g. interactions between the driver, infrastructure and the vehicle. Even though such micro level analysis are important, macro traffic safety policies can create more sustainable systems that pre-empt safety issues and reduce likelihood of traffic accidents. This paper presents two preliminary case studies of how SD can facilitate and encourage macro and meso levels traffic safety policy. In the first case study, a small SD model was created to assess the policy options to encourage purchase cars with higher safety rating. In the second case study, an existing SD simulation model that evaluates the impact of public transport policies on travel time is extended to include traffic safety consideration. The authors draw on the experience of developing the two hypothetical case studies to assess the usefulness and challenges of using SD to facilitate traffic safety policy.