利用自然实验研究评估英国两个主要城市每小时20英里的限速规定。
Use of natural experimental studies to evaluate 20mph speed limits in two major UK cities.
作者信息
Milton Karen, Kelly Michael P, Baker Graham, Cleland Claire, Cope Andy, Craig Neil, Foster Charlie, Hunter Ruth, Kee Frank, Kelly Paul, Nightingale Glenna, Turner Kieran, Williams Andrew J, Woodcock James, Jepson Ruth
机构信息
Norwich Medical School, University of East Anglia, UK.
Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge, UK.
出版信息
J Transp Health. 2021 Sep;22:101141. doi: 10.1016/j.jth.2021.101141.
INTRODUCTION
Reductions in traffic speed can potentially offer multiple health and public health benefits. In 2016, implementation of 20mph (30kph) speed limit interventions began in Edinburgh (city-wide) and Belfast (city centre). The aims of this paper are to describe 1) the broad theoretical approach and design of two natural experimental studies to evaluate the 20mph speed limits in Edinburgh and Belfast and 2) how these studies allowed us to test and explore theoretical mechanisms of 20mph speed limit interventions.
METHODS
The evaluation consisted of several work packages, each with different research foci, including the political decision-making processes that led to the schemes, their implementation processes, outcomes (including traffic speed, perceptions of safety, and casualties) and cost effectiveness. We used a combination of routinely and locally collected quantitative data and primary quantitative and qualitative data.
RESULTS
The evaluation identified many contextual factors influencing the likelihood of 20mph speed limits reaching the political agenda. There were substantial differences between the two sites in several aspects related to implementation. Reductions in speed resulted in significant reductions in collisions and casualties, particularly in Edinburgh, which had higher average speed at baseline. The monetary value of collisions and casualties prevented are likely to exceed the costs of the intervention and thus the overall balance of costs and benefits is likely to be favourable.
CONCLUSIONS
Innovative study designs, including natural experiments, are important for assessing the impact of 'real world' public health interventions. Using multiple methods, this project enabled a deeper understanding of not only the effects of the intervention but the factors that explain how and why the intervention and the effects did or did not occur. Importantly it has shown that 20mph speed limits can lead to reductions in speed, collisions and casualties, and are therefore an effective public health intervention.
引言
降低交通速度可能会带来多种健康和公共卫生益处。2016年，爱丁堡（全市范围）和贝尔法斯特（市中心）开始实施每小时20英里（30公里）的限速干预措施。本文旨在描述：1）两项自然实验研究的广泛理论方法和设计，以评估爱丁堡和贝尔法斯特每小时20英里的限速措施；2）这些研究如何使我们能够测试和探索每小时20英里限速干预措施的理论机制。
方法
评估包括几个工作包，每个工作包都有不同的研究重点，包括导致这些方案的政治决策过程、其实施过程、结果（包括交通速度、安全认知和伤亡情况）以及成本效益。我们结合了常规收集和本地收集的定量数据以及原始定量和定性数据。
结果
评估确定了许多影响每小时20英里限速措施进入政治议程可能性的背景因素。在与实施相关的几个方面，两个地点存在很大差异。速度降低导致碰撞和伤亡显著减少，特别是在爱丁堡，其基线平均速度较高。避免的碰撞和伤亡的货币价值可能超过干预成本，因此成本效益的总体平衡可能是有利的。
结论
包括自然实验在内的创新研究设计对于评估“现实世界”公共卫生干预措施的影响很重要。通过使用多种方法，该项目不仅能够更深入地了解干预措施的效果，还能了解解释干预措施如何以及为何产生或未产生效果的因素。重要的是，它表明每小时20英里的限速措施可以降低速度、碰撞和伤亡，因此是一种有效的公共卫生干预措施。
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