Department of Civil and Environmental Engineering, The Pennsylvania State University, 231 Sackett Building, University Park, PA 16802, United States.
Accid Anal Prev. 2020 Sep;144:105672. doi: 10.1016/j.aap.2020.105672. Epub 2020 Jul 8.
Adaptive traffic signal control (ATSC) is a novel traffic management system that is often deployed at high-volume intersections in order to mitigate traffic congestion and improve travel time reliability. While past studies have demonstrated its operational effectiveness, relatively few have focused on safety performance. Those that have tend to suffer from limitations including small sample sizes, insufficient study designs, or the lack of consideration of potential temporal and corridor effects after ATSC installation. Furthermore, results from previous studies are mixed: while many studies point to a safety improvement, more recent studies seem to indicate that ATSC systems might increase crash frequency. In light of this, a comprehensive Empirical Bayes (EB) before-after observational study was conducted using ATSC data collected throughout Pennsylvania. Crash modification factors (CMFs) were estimated based on the following different case scenarios: crash severity levels and crash types (total, fatal and injury, rear-end, and angle crashes); intersection locations (all intersections and intersections along corridors only); and, intersection configurations (3-leg and 4-leg). Temporal trends for intersection-level CMFs were examined using annual crash data in the after period. Corridor-level CMFs were also developed to quantify changes in safety performance along corridors with ATSC installed. The results suggest that ATSC is associated with a nominal increase in total and angle crashes, and an expected decrease in fatal plus injury crashes and rear-end crashes. However, the results were not statistically significant. The safety effect estimates are similar when considering intersection locations and configurations. In addition, the temporal trend analysis indicates that the safety effectiveness does not vary annually in the after period, suggesting no obvious novelty effect associated with ATSC. Finally, the magnitude of the corridor-level CMFs are slightly lower than the intersection-level CMFs, except for rear-end crashes.
自适应交通信号控制（ATSC）是一种新颖的交通管理系统，通常部署在交通量较大的交叉口，以减轻交通拥堵并提高旅行时间可靠性。虽然过去的研究已经证明了其运行效果，但很少有研究关注其安全性能。那些研究往往存在样本量小、研究设计不足或缺乏对 ATSC 安装后潜在的时间和走廊效应的考虑等局限性。此外，先前研究的结果参差不齐：虽然许多研究表明安全性有所提高，但最近的研究似乎表明 ATSC 系统可能会增加事故频率。有鉴于此，使用宾夕法尼亚州收集的 ATSC 数据，进行了一项全面的实证贝叶斯（EB）前后观察研究。根据以下不同案例情景估计了事故修正系数（CMF）：事故严重程度级别和事故类型（总事故、致命事故和伤害事故、追尾事故和角度事故）；交叉口位置（所有交叉口和仅沿走廊的交叉口）；以及交叉口配置（三向交叉口和四向交叉口）。使用后期间的年度事故数据检查了交叉口级别 CMF 的时间趋势。还开发了走廊级别 CMF，以量化安装 ATSC 后走廊的安全性能变化。结果表明，ATSC 与总事故和角度事故的名义增加以及致命事故和伤害事故以及追尾事故的预期减少相关。然而，结果并不具有统计学意义。当考虑交叉口位置和配置时，安全效果估计是相似的。此外，时间趋势分析表明，后期间安全效果每年没有变化，这表明与 ATSC 相关的新颖效应不明显。最后，除了追尾事故外，走廊级别 CMF 的幅度略低于交叉口级别 CMF。
