美国交通信号配时实践与技术综述

交通信号控制是城市交通管理的重要组成部分。交通信号配时优化作为一项投入规模较 小、效果较为明显的交通治理措施，近年来受到了广泛关注。美国是世界上较早应用交通信号控 制的国家，对其交通信号配时实践与技术进行分析具有重要借鉴意义。本文从实践角度出发，综 述了美国交通信号配时的技术特点、工作流程、主要配时工具以及近期研究动向。首先，将美国交 通信号配时的技术特点归纳为3点，即配时参数定义自成体系，强调感应控制条件下的信号协调和 采用“环栅相位结构”表示配时方案。其次，依据“结果导向”式的信号配时步骤归纳了美国信号配 时工作主要流程，同时分析了 Synchro，TRANSYT-7F，TranSync，Tru-Traffic 等信号配时软件工 具。另外，围绕“信号配时效果评价”“智能网联条件下的交通信号控制”两项主题介绍了近期美国 交通信号控制的研究动向。最后讨论了未来交通信号配时技术的发展并提出4点展望和关注，分 别是配时软件工具开发与应用将发挥日益重要的作用，新数据资源的应用将能够极大程度上改进 现有交通信号配时实践并带来显著工程效益，面向传统交通信号控制向智能网联环境过渡阶段的 配时研究需要加强，以及交通信号控制相关的基础性交通研究仍需进一步深入和巩固。

A Comprehensive Review of Traffic Signal Timing Practice and Techniques in the United States

Traffic signal control is a critical part of urban transportation management. As a cost-effective approach to traffic operational improvements, facilitating the development of signal timing has been of a great interest to traffic engineers and researchers in recent years. The United States (US) is one of the most advanced countries where traffic signals were first implemented, and its best practices and lessons learned could be beneficial to many other countries. This paper provides a comprehensive review of traffic signal timing practice and techniques in the US, focusing on signal control characteristics, timing development process and software tools, as well as emerging technologies and techniques. The signal control practice in the US (also Canada) possesses some unique characteristics comparing to other countries. First, some signal timing terminologies may only exist in the US or have different meanings, such as a “signal phase”. Those who are interested in understanding the US practice must go through the details of the term definitions documented in the US manuals and standards. Secondly, a special ring-barrier structure is widely adopted to describe signal phasing and timing. Through a combination of rings and barriers that imply the duration, sequence and compatibility of signal phases, this structure allows for safe and efficient implementation of signal timing, especially at typical intersections with actuated traffic signals. Thirdly, the US signal control facilities and signal timing techniques are mostly on traffic actuated control. In the context of an actuated control mode, timing development for isolated signals can be simplified, as signal operations are largely in response to detector actuations; hence, the major effort goes to developing signal coordination.An outcome-based procedure has been highly encouraged in the US signal timing development process. The procedure is comprised of several steps, such as data collection, data analysis, timing development, and timing maintenance, in which the effectiveness and efficiency of signal timing development must rely on advanced software tools. In this paper, five signal timing software tools are analyzed regarding features of data management, timing optimization, timing diagnosis, and performance evaluation. While all of these software tools have basic functions of signal timing optimization and data management, some major differences exist in terms of timing diagnosis and performance evaluation. Timing diagnosis is important for identifying erroneous and abnormal signal operations, which ensures consistency between the designed timing plans and actual field operations. The mobile version of TranSync features active time- space diagrams and visualization of ring- barrier- strucature- based signal operations, allowing for convenient timing diagnosis in the field. Performance measurement is needed for monitoring the quality of signal timing and validating the effectiveness of signal re- timing. Earlier software packages, such as TRANSYT- 7F, PASSER and Synchro, only provide performance evaluation functions based on deterministic algrithoms and simulation, while emerging tools such as Tru- Traffic and TranSync allow users to collect actual travel- run trajectories and produce performance evaluations accordingly. The signal timing practice and techniques in the US are transforming along with the emerging technologies. Numerous studies have been conducted in recent years, and two topics are highlighted in this review, i.e., traffic signal performance meansures based on new data sources and new signal control methodologies considering a connected-andautonomous- vehicles (CAV) environment. In recent years, a variety of data sources have been used to assess traffic control performance. Automated Traffic Signal Performance Measures (ATSPMs) is an influential research effort that incorporates high-resolution controller and detector event data to gauge traffic control efficieny such as the quality of platoon progression. Travel-run trajectory data are also used in some studies to evaluate signal coordination according to travel time and the number of stops. A vast number of studies are conducted on the second topic, investigating the impacts of future CAV applications and formulating many possibilities of next- generation traffic signal control. In addition to the two topics, a few studies are devoted to improving the classic signal timing optimization algorithms. The improvements are aimed at signal coordination for multimodal traffic and special cases. Lastly, this paper provides an outlook for future signal timing practice and techniques. Signal timing tools will continue to play an important role in satisfying complex traffic management strategies and goals. The innovative use of multi-source data will enhance the traffic timing process in terms of performance monitoring. The application of CAV technologies may lead to a revolution of signal control; however, a dramatic change of the current signal control infrastructure is unlikely in the near future due to the immaturity of the current research and the mixed driving environment during a transition stage. As a result, it advocates studies for improving traffic signal timing during the transition stage towards a complete CAV circumstance. Research efforts are also required for developing necessary updates for the classic signal timing theories that were established decades ago.