Queensland University of Technology, School of Civil and Environmental Engineering, Brisbane, Australia.
Queensland University of Technology, Centre for Accident Research and Road Safety - Queensland (CARRS-Q), Brisbane, Australia.
Accid Anal Prev. 2022 Feb;165:106527. doi: 10.1016/j.aap.2021.106527. Epub 2021 Dec 7.
The Empirical Bayes approach for before-after evaluation methodology utilizing the negative binomial model does not account well for unobserved heterogeneity. Building on the Empirical Bayes approach, the objective of this study was to propose a framework to accommodate unobserved heterogeneity in before-after countermeasure evaluation. In particular, this study has proposed a simulation-based Empirical Bayes approach by applying the panel random parameters negative binomial model with parameterized overdispersion (PRNB-PO) to evaluate the effectiveness of engineering treatments. The proposed framework has been tested for the wide centerline treatment (WCLT) on rural two-lane two-way highways in Australia. The empirical analysis included 511 km of WCLT treated highways in a before-after evaluation within a time period of 2010 - 2018 and 430 km of reference sites in Queensland, Australia. The PRNB-PO models outperformed the traditional negative binomial models in terms of goodness-of-fit and prediction performance for total injury crashes, and fatal and serious injury (FSI) crashes. The simulation-based Empirical Bayes approach using the PRNB-PO model resulted in more precise estimates of crash modification factors than the standard Empirical Bayes approach. The WCLT is found to result in significant reductions in total injury crashes by 28.21% (95% confidence interval (CI) = 22.92 - 33.50%), FSI crashes by 13.90% (95% CI = 6.99 - 20.81%), and head-on crashes by 25.45% (95% CI = 14.87 - 36.03%). Overall, WCLT is an effective engineering treatment and should be considered a low-cost countermeasure on rural two-lane two-way highways.
利用负二项模型的前后评估方法的经验贝叶斯方法不能很好地解释未观测到的异质性。本研究基于经验贝叶斯方法，旨在提出一种框架，以适应前后对策评估中未观察到的异质性。特别是，本研究通过应用带有参数过分散（PRNB-PO）的面板随机参数负二项模型（PRNB-PO）提出了一种基于模拟的经验贝叶斯方法，以评估工程措施的有效性。该框架已在澳大利亚农村双车道双向公路的宽中线处理（WCLT）中进行了测试。实证分析包括在 2010-2018 年期间对澳大利亚昆士兰州的 511 公里 WCLT 处理公路和 430 公里参考路段进行前后评估。PRNB-PO 模型在总伤害事故和致命和严重伤害（FSI）事故的拟合优度和预测性能方面均优于传统的负二项模型。基于 PRNB-PO 模型的模拟经验贝叶斯方法得出的碰撞修正因子估计值比标准经验贝叶斯方法更精确。结果表明，WCLT 可使总伤害事故减少 28.21%（95%置信区间（CI）=22.92-33.50%），FSI 事故减少 13.90%（95%CI=6.99-20.81%），正面碰撞事故减少 25.45%（95%CI=14.87-36.03%）。总的来说，WCLT 是一种有效的工程措施，应被视为农村双车道双向公路的低成本对策。
