Glenn Department of Civil Engineering, Clemson University, Clemson, SC 29634, USA.
Applied Statistics, School of Mathematical and Statistical Sciences, Clemson University, Clemson, SC 29634, USA.
J Safety Res. 2021 Feb;76:314-326. doi: 10.1016/j.jsr.2020.12.020. Epub 2021 Jan 12.
Reducing the likelihood of freeway secondary crashes will provide significant safety, operational and environmental benefits. This paper presents a method for assessing the likelihood of freeway secondary crashes with Adaptive Signal Control Systems (ASCS) deployed on alternate routes that are typically used by diverted freeway traffic to avoid any delay or congestion due to a freeway primary crash.
The method includes four steps: (1) identification of secondary crashes, (2) verification of alternate routes, (3) assessment of the likelihood of secondary crashes for freeways with ASCS deployed on alternate routes and non-ASCS (i.e. pre-timed, semi- or fully-actuated) alternate routes, and (4) investigation of unobserved heterogeneity of the likelihood of freeway secondary crashes. Four freeway sections (i.e., two with ASCS deployed on alternate routes and two non-ASCS alternate routes) in South Carolina are considered.
Findings from the logistic regression modeling reveal significant reduction in the likelihood of secondary crashes for one freeway section (i.e., Charleston I-26 E) with ASCS deployed on alternate route. Other factors such as rear-end crash, dark or limited light, peak period, and annual average daily traffic contribute to the likelihood of freeway secondary crashes. Furthermore, random-parameter logistic regression model results for Charleston I-26 E reveal that unobserved heterogeneity of ASCS effect exists across the observations and ASCS are associated with the reduction of the likelihood of freeway secondary crashes for 84% of the observations (i.e., primary crashes). Location of the primary crash on the freeway is observed to affect the benefit of ASCS toward freeway secondary crash reduction as the primary crash's location determines how many upstream freeway vehicles will be able to take the alternate route. Practical Applications: Based on the findings, it is recommended that the South Carolina Department of Transportation (SCDOT) considers deploying ASCS on alternate routes parallel to freeway sections where high percentages of secondary crashes are found.
降低高速公路二次事故的可能性将带来显著的安全、运行和环境效益。本文提出了一种利用自适应信号控制系统（ASCS）评估在替代路线上发生高速公路二次事故可能性的方法，这些替代路线通常被分流的高速公路交通用于避开由于高速公路主线事故而导致的任何延误或拥堵。
该方法包括四个步骤：（1）识别二次事故，（2）验证替代路线，（3）评估部署在替代路线和非 ASCS（即定时、半或全激活）替代路线上的高速公路发生二次事故的可能性，以及（4）调查高速公路二次事故可能性的未观测异质性。南卡罗来纳州的四条高速公路路段（两条部署了 ASCS 的替代路线和两条非 ASCS 的替代路线）被考虑在内。
逻辑回归模型的结果表明，部署在替代路线上的 ASCS 显著降低了一条高速公路路段（即查尔斯顿 I-26 E）发生二次事故的可能性。其他因素，如追尾事故、黑暗或有限的光线、高峰时段和年平均日交通量，也会增加高速公路二次事故的可能性。此外，查尔斯顿 I-26 E 的随机参数逻辑回归模型结果表明，ASCS 的效果存在未观测到的异质性，且 ASCS 与降低 84%的观测到的高速公路二次事故的可能性相关（即主线事故）。高速公路上主线事故的位置被观察到会影响 ASCS 对减少高速公路二次事故的效果，因为主线事故的位置决定了有多少上游高速公路车辆能够使用替代路线。
根据研究结果，建议南卡罗来纳州交通部（SCDOT）考虑在发现二次事故比例较高的高速公路路段的平行替代路线上部署 ASCS。
