The policymaking dynamics of adopting speed limit reductions: a system dynamics approach

Background: Efforts such as Health-for-All Policies acknowledge that including health in policies improves public health and has co-benefits. Transport policy is an opportunity to include promote public health. However, the specific policy dynamics that lead to policy enactment and those that precede these decisions are not well understood.

Purpose: We aimed to identify the dynamics and factors involved in decision making, using the case of 20 miles per hour (mph) speed limits, and the role of dynamics and factors as being facilitative and/or obstructive.

Methods: In this qualitative study, 13 semi-structured interviews were carried out among 5 policy makers, 5 researchers and 3 advocates from UK, Switzerland, Spain, Ireland and Austria in cities that successfully implemented 20mph limits. Data was coded in MAXQDA according to barriers and facilitators of policy dynamics. We created a causal loop diagram (CLD) to identify reinforcing and balancing feedback loops in order to understand policy dynamics of successful policy enactment.

Results: Data saturation was reached after 9 interviews. The CLD provided insight in balancing dynamics including measurement and evaluation and political leadership. For example, a balancing feedback loop around measurement and evaluation suggested that data collection and evaluation during incremental policy implementation might decrease the fear of unwanted outcomes among opposition groups, which in turn could decrease the policy makers’ fear of the public’s reaction and has the potential to increase the political leadership to implement these policies. Moreover, reinforcing feedback loops were identified around public acceptance and topic normalization.

Conclusions: These insights help to understand the dynamics underlying successful policy enactment and to identify key stakeholder groups to enhance policy enactment.

Policy implications: Incremental policy implementation could lead to higher public acceptance, reducing policy makers fear and potentially increase their leadership to implement policies.

Funding: Vital Cities and Citizens Initiative of Erasmus University Rotterdam