Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Lyles School of Civil Eng., Purdue University, W. Lafayette, IN, USA; Robotics Institute, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.
Accid Anal Prev. 2021 May;154:106089. doi: 10.1016/j.aap.2021.106089. Epub 2021 Mar 24.
In previous research, the effects of commercial vehicle proportions (CVP) on overall crash propensity have been found to be significant, but the results have been varied in terms of the effect direction. In addition, the mediating or moderating effects of roadway attributes on the CVP-vs-safety relationships, have not been investigated. In addressing this gap in the literature, this study integrates databases on crashes, traffic, and inventory for Hong Kong road segments spanning 2014-2017. The classes of commercial vehicles considered are public buses, taxi, and light-, medium- and heavy-goods vehicles. Random-parameter Tobit models were estimated using the crash rates. The results suggest that the CVP of each class show credible effects on the crash rates, for the various crash severity levels. The results also suggest that the interaction between CVP and roadway attributes is credible enough to mediate the effect of CVP on crash rates, and the magnitude and direction of such mediation varies across the vehicle classes, crash severity levels, and roadway attribute type in four ways. First, the increasing effect of taxi proportion on slight-injury crash rate is magnified at road segments with high intersection density. Second, the increasing effect of light-goods vehicle proportion on slight-injury crash rate is magnified at road segments with on-street parking. Third, the association between the medium- and heavy-goods vehicle proportion and killed/severe injury (KSI) crash rate, is moderated by the roadway width (number of traffic lanes). Finally, a higher proportion of medium- and heavy-goods vehicles generally contributes to increased KSI crash rate at road segments with high intersection density. Overall, the findings of this research are expected not only to help guide commercial vehicle enforcement strategy, licensing policy, and lane control measures, but also to review existing urban roadway designs to enhance safety.
在先前的研究中，已发现商用车辆比例（CVP）对整体碰撞倾向的影响显著，但在影响方向上结果存在差异。此外，道路属性对 CVP 与安全性关系的中介或调节作用尚未得到研究。为了解决文献中的这一空白，本研究整合了香港道路路段 2014-2017 年的碰撞、交通和清单数据库。所考虑的商用车辆类别包括公共巴士、出租车以及轻型、中型和重型货车。使用碰撞率估计了随机参数 Tobit 模型。结果表明，各车辆类别的 CVP 对各种碰撞严重程度级别的碰撞率具有可信的影响。结果还表明，CVP 与道路属性之间的相互作用足以调节 CVP 对碰撞率的影响，并且这种调节的幅度和方向在四种方式上因车辆类别、碰撞严重程度级别和道路属性类型而异。首先，在交叉口密度较高的路段，出租车比例对轻伤碰撞率的递增影响会放大。其次，在有路边停车的路段，轻型货车比例对轻伤碰撞率的递增影响会放大。第三，在道路宽度（车道数量）的调节下，中型和重型货车比例与死亡/重伤（KSI）碰撞率之间的关联发生变化。最后，在交叉口密度较高的路段，较高比例的中型和重型货车通常会导致 KSI 碰撞率增加。总体而言，本研究的发现不仅有望帮助指导商用车辆执法策略、许可政策和车道控制措施，还将审查现有的城市道路设计以提高安全性。
