Department of Civil & Architectural Engineering, University of Wyoming, Office: EN 3084, 1000 E University Avenue, Laramie, WY 82071, United States.
Department of Civil & Architectural Engineering, University of Wyoming, 1000 E University Avenue, Laramie, WY 82071, United States.
J Safety Res. 2019 Feb;68:107-118. doi: 10.1016/j.jsr.2018.12.006. Epub 2018 Dec 17.
The state of Wyoming, like other western United States, is characterized by mountainous terrain. Such terrain is well noted for its severe downgrades and difficult geometry. Given the specific challenges of driving in such difficult terrain, crashes with severe injuries are bound to occur. The literature is replete with research about factors that influence crash injury severity under different conditions. Differences in geometric characteristics of downgrades and mechanics of vehicle operations on such sections mean different factors may be at play in impacting crash severity in contrast to straight, level roadway sections. However, the impact of downgrades on injury severity has not been fully explored in the literature. This study is thus an attempt to fill this research gap. In this paper, an investigation was carried out to determine the influencing factors of crash injury severities of downgrade crashes.
Due to the ordered nature of the response variable, the ordered logit model was chosen to investigate the influencing factors of crash injury severities of downgrade crashes. The model was calibrated separately for single and multiple-vehicle crashes to ensure the different factors influencing both types of crashes were captured.
The parameter estimates were as expected and mostly had signs consistent with engineering intuition. The results of the ordered model for single-vehicle crashes indicated that alcohol, gender, road condition, vehicle type, point of impact, vehicle maneuver, safety equipment use, driver action, and annual average daily traffic (AADT) per lane all impacted the injury severity of downgrade crashes. Safety equipment use, lighting conditions, posted speed limit, and lane width were also found to be significant factors influencing multiple-vehicle downgrade crashes. Injury severity probability plots were included as part of the study to provide a pictorial representation of how some of the variables change in response to each level of crash injury severity.
Overall, this study provides insights into contributory factors of downgrade crashes. The literature review indicated that there are substantial differences between single- and multiple vehicle crashes. This was confirmed by the analysis which showed that mostly, separate factors impacted the crash injury severity of the two crash types. Practical applications: The results of this study could be used by policy makers, in other locations, to reduce downgrade crashes in mountainous areas.
怀俄明州与美国西部其他州一样，以山区地形为特征。这种地形以陡峭的下坡和复杂的几何形状而闻名。考虑到在这种困难地形中驾驶的特殊挑战，严重受伤的事故必然会发生。文献中充满了关于不同条件下影响碰撞伤害严重程度的因素的研究。下坡的几何特征和车辆在这些路段上的操作力学的差异意味着，与直线路段相比，不同的因素可能会对碰撞严重程度产生影响。然而，下坡对伤害严重程度的影响在文献中尚未得到充分探讨。因此，本研究试图填补这一研究空白。本文旨在研究下坡事故碰撞伤害严重程度的影响因素。
由于因变量的有序性质，选择有序逻辑回归模型来研究下坡事故碰撞伤害严重程度的影响因素。为了确保同时捕捉到影响这两种类型事故的不同因素，分别为单车事故和多车事故校准了模型。
参数估计值符合预期，且大多具有与工程直觉一致的符号。单车事故有序模型的结果表明，酒精、性别、道路状况、车型、碰撞点、车辆操作、安全设备使用、驾驶员行为以及每车道的年平均日交通量（AADT）都影响了下坡事故的伤害严重程度。安全设备使用、照明条件、限速和车道宽度也被发现是影响多车下坡事故的重要因素。作为研究的一部分，还包括了伤害严重程度概率图，以直观地展示一些变量如何随着每个碰撞伤害严重程度级别的变化而变化。
总的来说，本研究提供了下坡事故的促成因素的见解。文献综述表明，单车事故和多车事故之间存在很大差异。分析结果证实了这一点，即大多数情况下，不同的因素影响了这两种事故类型的碰撞伤害严重程度。实际应用：这项研究的结果可被决策者用于减少山区下坡事故。
