The effectiveness of a 20 mph speed limit intervention on vehicle speeds in Bristol, UK: A non-randomised stepped wedge design

摘要: © 2018 Elsevier Ltd Twenty mph (32.2 km/h) speed limits across urban areas are becoming a widespread tool for public health and road danger reduction globally. Determining the effectiveness of these interventions on motorised vehicle speeds is crucial first step in any logic model that seeks to associate 20 improved wellbeing outcomes. However, little known about how introduction affects speeds. This paper presents findings from novel comprehensive academic evaluation adjusted effects sign-only city-wide intervention based natural experiment took place Bristol, UK. Applying quasi-stepped wedge design, 36,973,090 single vehicles, recorded by Automatic Traffic Counts before after intervention, were analysed. Generalized linear mixed models used control confounding variables. Results showed an unadjusted 4.7 (7.56 2.66 (4.28 over two three years. Some variability due time variables was detected, with reductions being larger during night time, at weekends, summer months. The roads did not receive also saw small (0.03 mph). indicate successful lowering individual Policy makers encouraged implement careful monitoring limit order enable meaningful potential benefits.