Is 20 Plenty For Health? Methods for an evaluation of the 20 mph/30kph speed limit in Edinburgh and Belfast on a range of public health outcomes

Abstract

Transport has the potential to promote health, through enabling greater access and encouraging physical activity, and also to impact on health negatively, through causing road traffic collisions and influencing exposure to noise and air pollution. A range of methods and approaches are used in the evaluation. 1. Natural experimental, and before and after designs are used to evaluate effectiveness on a range of outcomes including: casualties; cycling and walking; driver perceptions and behaviours; and liveability. Quantitative data for evaluating effectiveness are drawn from a range of sources including Local Authorities, Sustrans (a sustainable transport charity), Routine Police Data and researcher collected data. 2. Qualitative methods (interviews and focus groups) are employed to: test and refine the programme theory; explore implementation; and learn more about transferability to different settings. Documentary analyses and social media analyses are also used to add to our understanding of key drivers and factor involved in decisions to implement speed limits in other parts of the UK, and whether they were successful or not. 3. Modelling and economic methods are used to test cost-effectiveness. We will present an overview of the methods used and some of the challenges of undertaking such a complex evaluation of a communitywide public health intervention.