Abstract：
Using data from a developing country, the current study develops a copula-based joint modeling framework to study crash type and driver injury severity as two dimensions of the severity process. To be specific, a copula-based multinomial logit model (for crash type) and generalized ordered logit model (for driver severity) is estimated in the study. The data for our analysis is drawn from Bangladesh for the years of 2000 to 2015. Given the presence of multiple years of data, we develop a novel spline variable generation approach that facilitates easy testing of variation in parameters across time in crash type and severity components. A comprehensive set of independent variables including driver and vehicle characteristics, roadway attributes, environmental and weather information, and temporal factors are considered for the analysis. The model results identify several important variables (such as driving under the influence of drug and alcohol, speeding, vehicle type, maneuvering, vehicle fitness, location type, road class, road geometry, facility type, surface quality, time of the day, season, and light conditions) affecting crash type and severity while also highlighting the presence of temporal instability for a subset of parameters. The superior model performance was further highlighted by testing its performance using a holdout sample. Further, an elasticity exercise illustrates the influence of the exogenous variables on crash type and injury severity dimensions. The study findings can assist policy makers in adopting appropriate strategies to make roads safer in developing countries.
摘要：
利用发展中国家的数据，当前的研究开发了一个基于copula的关节建模框架来研究碰撞类型和驾驶员伤害严重程度作为严重程度过程的两个维度。具体而言,研究中估计了基于copula的多项Logit模型（用于碰撞类型）和广义有序Logit模型（用于驾驶员严重程度）。我们分析的数据来自孟加拉国2000年至2015年。鉴于存在多年的数据，我们开发了一种新颖的样条变量生成方法，该方法有助于轻松测试碰撞类型和严重性组件中参数随时间的变化。一套全面的独立变量，包括驾驶员和车辆特征，道路属性,环境和天气信息，分析考虑了时间因素。模型结果确定了几个重要变量(如在药物和酒精的影响下驾驶，超速,车辆类型,机动,车辆健身，位置类型,道路类,道路几何,设施类型,表面质量,一天的时间，季节,和光照条件）影响碰撞类型和严重程度，同时也突出了参数子集的时间不稳定性的存在。通过使用保持样品测试其性能，进一步突出了卓越的模型性能。Further,弹性练习说明了外生变量对碰撞类型和伤害严重程度维度的影响。研究结果可以帮助决策者采取适当的战略，使发展中国家的道路更安全。
