IIHR-Hydroscience & Engineering, The University of Iowa, Iowa City, IA, USA.
IIHR-Hydroscience & Engineering, The University of Iowa, Iowa City, IA, USA.
Accid Anal Prev. 2019 Sep;130:22-29. doi: 10.1016/j.aap.2018.01.023. Epub 2018 Apr 23.
Numerous studies have examined the influence of rainfall on the relative risk of crash, and they all agree that rainfall leads to an increase in relative risk as compared to dry conditions; what they do not agree on is the magnitude of these increases. Here we consider three methodological decisions made in computing the relative risk and examine their impacts: the inclusion or exclusion of zero total events (where no crashes occur during event or control periods), the temporal scale of analysis, and the use of information on pavement and weather conditions contained with the crash reports to determine relative risk. Our analyses are based on several years of data from six U.S. states (Arkansas, Georgia, Illinois, Maryland, Minnesota and Ohio). Zero total events in the context of weather related crash studies typically provide no information on the actual crash odds and greatly alter the distribution of relative risk estimates and should be removed from the analysis. While the use of a daily time step provides an estimate of relative risk that is not significantly different from an hourly time step for the majority of rural counties in our study area, the same is true of only 39% of the urban counties. Finally, the use of pavement and weather condition information from the crash reports results in relative risk estimates that are lower than the standard approach, however this difference decreases as rainfall totals increase. By highlighting the influence of methodological choices, we hope to pave the way towards the potential reduction in uncertainties in weather-related relative risk estimates.
许多研究都考察了降雨对碰撞相对风险的影响，它们都同意降雨会导致相对风险增加，与干燥条件相比；他们不同意的是这些增加的幅度。在这里，我们考虑了在计算相对风险时做出的三个方法学决策，并研究了它们的影响：是否包括或排除零总事件（即事件或对照期内没有发生碰撞）、分析的时间尺度以及使用包含在碰撞报告中的路面和天气条件信息来确定相对风险。我们的分析基于来自六个美国州（阿肯色州、佐治亚州、伊利诺伊州、马里兰州、明尼苏达州和俄亥俄州）的多年数据。在与天气相关的碰撞研究中，零总事件通常无法提供实际碰撞几率的信息，并且会极大地改变相对风险估计的分布，因此应从分析中删除。虽然每日时间步长的使用提供了与我们研究区域的大多数农村县的小时时间步长没有显著差异的相对风险估计，但这种情况在城市县中仅为 39%。最后，使用碰撞报告中的路面和天气条件信息会导致相对风险估计值低于标准方法，但随着降雨量的增加，这种差异会减小。通过强调方法选择的影响，我们希望为减少与天气相关的相对风险估计的不确定性铺平道路。
