左转过饱和考虑相位均衡的信号配时优化研究

提出在保障交叉口总体效益最优和考虑驾驶员对红灯时长容忍度的前提下，设置逆向可变车道达到降低交叉口延误和提升通行能力。以各相位有效绿灯时长为优化变量，建立交叉口信号配时优化模型，并采取MOEA/D算法进行求解，结合设计案例，利用VISSIM7.0仿真软件在单位时长下对比优化前后各相位车均延误、车均排队长度和通行能力。求解的有效绿灯时长为19s、16s、15s、16s，有效验证了均衡相位绿灯时长的假设；仿真结果表明，车均延误平均下降26.15%；车均排队长度平均下降76.84%；通行能力平均提升约11.39%。提出的方法在降低交叉口延误，提升通行能力同时，能够均衡分配各相位有效绿灯时长，进而降低驾驶员等待红灯的焦虑感。     

多目标优化的公交被动优先信号配时模型

从公交信号优先的原则出发,考虑公交到达率的不确定性对周期长度、绿灯时间等合理调整,针对多路公交车共用同一公交专用道情况,提出以人均总延误最小为目标,分别以绿灯时间差模型和Webster最佳周期模型为信号配时计算模型计算交叉口信号配时参数,选取两者中造成人均延误最小的结果作为最终信号配时方案的计算方法。另外,除采用原有Webster最佳周期计算模型进行信号配时计算,还结合随机机会约束规划方法提出了以各相位绿灯时间与所需绿灯时间差绝对值之和最小为目标的绿灯时间差模型,通过随机模拟与微粒群算法的结合,给出了求解随机机会约束规划的新算法。以设有公交专用道的两相位信号交叉口为例设计算例,结果证明,公交车到达率的随机变化特性对于其所在交叉口信号配时参数的设置有明显影响,验证了公交被动优先对交叉口信号配时参数动态调整的有效性。本文模型根据被动优先中调整了周期时长及绿信比策略确定更优信号配时方案,相较仅以Webster最佳周期模型为依据计算人均延误的传统模型,最小人均延误模型平均降低了8. 12%的人均延误,证明了最小人均延误模型的有效性。说明最小人均延误模型可更好描述公交车到达率的波动性,降低对社会车辆负面影响,达到减少人均延误,提高交叉口通行效率的目的。     

倒计时对信号交叉口的安全影响分析

为研究倒计时对信号交叉口的安全影响,通过与无倒计时交叉口的驾驶行为进行对比,从违章及困境区域两方面分析倒计时对信号交叉口的安全影响。     

基于模糊控制的双交叉口相序可变信号配时方法

为优化交叉口信号配时,降低车辆平均延误,提出了一种相序可变的干线双交叉口模糊协调控制方法。提出的模糊协调控制方法包括候选相位选择控制器、绿灯相位观测控制器、相位切换控制器和两个交叉口协调控制模块共五个控制模块。相序可变的干线双交叉口模糊协调控制方法基于对当前上下游交叉口交通紧迫程度的判断,以及对未来交通状态演变的估计,采用相序可变的模糊控制方法实时、动态调整交叉口信号配时方案。利用MATLAB对VISSIM二次开发搭建仿真平台,对所提出的模糊控制方法进行了验证。结果表明,所提出的模糊控制方法在单交叉口和双交叉口两个控制层面均优于传统定时控制方法,可以显著降低车辆平均延误,提高交叉口通行效率。     

基于公交专用进口道的交叉口信号配时优化设计研究

本文研究设置公交专用进口道的城市交叉口信号配时,综合考虑社会车辆的运行,实现信号配时的公交优先与人均延误最小化。本文运用延误三角形及其相关理论建立延误模型,推导出人均延误函数,为公交优先单点定时控制提供了优化算法。同时本文利用VisualC仿真模型与改进算法对城市具体交叉口信号最佳周期及有效绿灯时间进行优化设计。     

非灯控交叉口交通安全状况评价

非灯控交叉口是交通流中的节点,对非灯控交叉口的交通安全状况进行评价具有导向性意义。文章针对交叉口管控存在的问题,提出了交通安全状况评价原则和主要方法,阐述了非灯控交叉口交通安全的影响因素,并通过对沈阳市刘家窑十字交叉口进行交通安全状况评价,提出了具体的交叉口交通安全改善措施,以提高非灯控交叉口的交通安全性。     

不完全车联网环境下单交叉口信号配时方法

车联网技术的发展给城市信号控制带来了机遇，但是车联网环境建设需要一段较长的时间，本文将车联网发展过程中智能网联车和非网联车混行的过渡阶段称为不完全车联网环境。针对不完全车联网环境下城市孤立交叉口信号配时问题，提出了基于双环相位进行相序优化的模糊控制方法。该方法基于双环相位对相序进行优化，模糊控制系统的输入为绿灯相位排队车辆数和红灯相位排队车辆数，输出绿灯延长时间。对SUMO仿真软件进行二次开发，实现该相序优化的模糊控制方法，并且将其与定时控制和模糊控制方法进行比较。仿真结果表明，当智能网联车和非智能网联车混行时，相序优化后的模糊控制方法能够有效的减少车辆的平均等待时间。     

平面信号控制交叉口交通优化设计方法研究 ——以盐城市胜利路与海阔路交叉口为例

通过对平面信号控制交叉口交通优化设计,对提高交叉口通行能力有着重要作用.本文以盐城市胜利路与海阔路交叉口为例,针对分析交叉口现状交通量、交叉口渠化现状、混合交通冲突点,信号配时现状,提出改善措施,提高交叉口的通行能力和安全水平.     

城市道路平面交叉口安全评价研究

城市平面交叉口是城市交通冲突和事故频繁发生的地点。文章针对城市道路平面交叉口的交通安全现状,分析了平面交叉口的安全影响因素,提出引入事故率和冲突率为评价指标,建立了灰色理论评价方法,为城市道路平面交叉口的安全治理提供理论支持。     

异形交叉口交通改善研究

本文针对现有异形交叉口存在的主要交通问题提出相应的改造原则,并以厦门市某交叉口为例,在交通量调查的基础下,结合交叉口渠化及信号配时研究对其进行提升研究,同时利用SYNCHRO仿真软件对改造后的交叉口延误进行评价,为类似交叉口改造提供相关经验.     

Vehicle actuated signal performance under general traffic at an isolated intersection

We study green extension of a two-phased vehicle actuated signal at an isolated intersection between two one-way streets. The green phase is extended by a preset time interval, referred to as critical gap, from the time of a vehicle actuation at an advance detector. The green phase switches if there is no arrival during the critical gap. We develop an exact model to study the intersection performance with traffic following Poisson processes. We further extend the model to approximate the case of general traffic. Our model in the general case works well compared with Monte Carlo simulation. A few major observations include: (1) The optimal critical gap decreases with the traffic; (2) The optimal critical gap can be much larger (up to 5 s) than the common presumption of 2–3 s; (3) Queue clearance policy is not nearly optimal in general even in the case of heavy traffic.     

Characterising Green Light Optimal Speed Advisory trajectories for platoon-based optimisation

Conceptually, a Green Light Optimal Speed Advisory (GLOSA) system suggests speeds to vehicles, allowing them to pass through an intersection during the green interval. In previous papers, a single speed is computed for each vehicle in a range between acceptable minimum and maximum values (for example between standstill and the speed limit). This speed is assumed to be constant until the beginning of the green interval, and sent as advice to the vehicle. The goal is to optimise for a particular objective, whether it be minimisation of emissions (for environmental reasons), fuel usage or delay. This paper generalises the advice given to a vehicle, by optimising for delay over the entire trajectory instead of suggesting an individual speed, regardless of initial conditions – time until green, distance to intersection and initial speed. This may require multiple acceleration manoeuvres, so the advice is sent as a suggested acceleration at each time step. Such advice also takes into account a suitable safety constraint, ensuring that vehicles are always able to stop before the intersection during a red interval, thus safeguarding against last-minute signal control schedule changes. While the algorithms developed primarily minimise delay, they also help to reduce fuel usage and emissions by conserving kinetic energy. Since vehicles travel in platoons, the effectiveness of a GLOSA system is heavily reliant on correctly identifying the leading vehicle that is the first to be given trajectory advice for each cycle. Vehicles naturally form a platoon behind this leading vehicle. A time loop technique is proposed which allows accurate identification of the leader even when there are complex interactions between preceding vehicles. The developed algorithms are ideal for connected autonomous vehicle environments, because computer control allows vehicles’ trajectories to be managed with greater accuracy and ease. However, the advice algorithms can also be used in conjunction with manual control provided Vehicle-to-Infrastructure (V2I) communication is available.     

Simultaneous control of traffic lights and bus departure for priority operation

This article presents a bus priority method for traffic light control based on two modes of operation: immediate and controlled departure. The immediate departure mode is a standard procedure in which the intersection controller grants priority upon request of the bus. Controlled departure acts to avoid a second stop of the bus at the end of the queue formed during red by holding the bus at the bus stop, while still granting priority to the bus lane. Selection of one of the two modes is based on intersection cost that includes bus delay and the impact on the overall traffic near the intersection. The method is applied in a constant cycle scenario where green recall and green extension can only be granted within certain limits. Numerical examples illustrate the application of the approach.     

A probabilistic approach to calculate capacity of signalized intersections with a red light camera

In recent years, red light cameras (RLCs) have been installed at many signalized intersections. The main reason behind installing RLCs is to reduce intersection‐related accidents caused because of a driver's behavior to cross the intersection when the signal turns red. By nature, if the driver is aware of the presence of RLC his or her driving behavior is bound to change. This behavioral change, however, may be intentional or unintentional. This may influence the utilization of yellow intervals resulting in a possible increase in dilemma zone, which in turn, may reduce the service capacity of the intersection. To accurately capture this capacity reduction, we present a probabilistic approach to modify the saturation flow rate formula in the Highway Capacity Manual that is currently used to calculate the capacity of signalized intersections. We introduce a new factor in the saturation flow rate calculation called red light reduction factor, to account for the capacity reduction owing to RLCs. Using field data from Baltimore, Maryland, we establish a relationship for the red light reduction factor. We then show that capacity of RLC‐equipped intersections is generally lower than that without RLCs. Although the percentage reduction in capacity of a single intersection may not seem significant, the cumulative impact of such reduction in a heavily traveled road network may be quite significant, resulting in significant loss in travel time. In future works, the systemwide capacity reduction owing to the presence of RLCs can be studied in congested transportation networks. Copyright © 2012 John Wiley & Sons, Ltd.     

A capacity maximization scheme for intersection management with automated vehicles

With the advent of connected and automated vehicle technology, in this paper, we propose an innovative intersection operation scheme named as MCross: Maximum Capacity inteRsection Operation Scheme with Signals. This new scheme maximizes intersection capacity by utilizing all lanes of a road simultaneously. Lane assignment and green durations are dynamically optimized by solving a multi-objective mixed-integer non-linear programming problem. The demand conditions under which full capacity can be achieved in MCross are derived analytically. Numerical examples show that MCross can almost double the intersection capacity (increase by as high as 99.51% in comparison to that in conventional signal operation scheme).     

Analysis of yellow-light running at signalized intersections using high-resolution traffic data

Many accidents occurring at signalized intersections are closely related to drivers’ decisions of running through intersections during yellow light, i.e., yellow-light running (YLR). Therefore it is important to understand the relationships between YLR and the factors which contribute to drivers’ decision of YLR. This requires collecting a large amount of YLR cases. However, existing data collection method, which mainly relies on video cameras, has difficulties to collect a large amount of YLR data. In this research, we propose a method to study drivers’ YLR behaviors using high-resolution event-based data from signal control systems. We used 8 months’ high-resolution data collected by two stop-bar detectors at a signalized intersection located in Minnesota and identified over 30,000 YLR cases. To identify the possible reasons for drivers’ decision of YLR, this research further categorized the YLR cases into four types: “in should-go zone”, “in should-stop zone”, “in dilemma zone”, and “in optional zone” according to the driver’s location when signal turns to yellow. Statistical analysis indicates that the mean values of approaching speed and acceleration rate are significantly different for different types of YLR. We also show that there were about 10% of YLR drivers who cannot run through intersection before traffic light turns to red. Furthermore, based on a strong correlation between hourly traffic volume and number of YLR events, this research developed a regression model that can be used to predict the number of YLR events based on hourly flow rate. This research also showed that snowing weather conditions cause more YLR events.     

Analysis of intersection delay under real-time adaptive signal control

The United States Department of Transportation has recently begun implementation of the national demonstration project for suburban Advanced Traffic Management Systems (ATMS) utilizing the Sydney Coordinated Adaptive Traffic System (SCATS). SCATS is an automated, real time, traffic responsive signal control strategy. The expected benefit from the system comes from its ability to constantly modify signal timing patterns to most effectively accommodate changing traffic conditions. The objectives of this research study were to analyze the differences in certain delay parameters which would occur as a result of implementing SCATS signal control. The study employed a macroscopic simulation procedure to compute intersection delay under both a strategy that changed signal timings once per hour and SCATS signal control. A comparison of delay under both forms of control is presented. The study findings demonstrated mixed results regarding the benefit of SCATS control. A general conclusion of the study was that SCATS distributed the delay across competing approaches more evenly. However, in some cases this resulted in an increase in the total intersection delay. The observed delay change was attributed primarily to the saturation equalization objective of the SCATS control program. SCATS attempts to allocate green time to the intersection approaches based on the degree of saturation. Under this philosophy the system is able to balance the percentage of green time between all approaches, resulting in more uniform delay.     

台州市信号灯交叉口碳排放测算及优化策略

近年来随着小汽车保有量的不断增多,机动车尾气成为碳排放的主要组成部分。文中以信号灯控制交叉口运行的小汽车为研究对象,通过研究小汽车在交叉口减速、怠速、加速三种工况下车辆的排放特性,将信号灯交叉口小汽车温室气体排放量量化。本文以台州市市府大道-中心大道交叉口为例,通过实地调查该交叉口当前平峰期和高峰期信号灯配时特性、交通运行特性等实际参数,对二氧化碳排放量进行测算,最终得出该交叉口在平峰期和高峰期的二氧化碳小时排放量,为后续该交叉口采取优化策略后在碳排放指标方面的量化效果提供参考依据,同时为台州市信号灯交叉口碳排放量测算提供参考方法。     

The symmetric intersection design and traffic control optimization

It is well recognized that the left-turning movement reduces the intersection capacity significantly, because exclusive left turn phases are needed to discharge left turn vehicles only. This paper proposes the concept of Left-Hand Traffic (LHT) arterial, on where vehicles follow left-hand traffic rules as in England and India. The unconventional intersection where a LHT arterial intersects with a Right-Hand Traffic (RHT) arterial is named as symmetric intersection. It is only need three basic signal phases to separate all conflicts at symmetric intersection, while it at least need four signal phases at a conventional intersection. So, compared with the conventional intersection, the symmetric intersection can provide longer green time for the left-turning and the through movement, which can increase the capacity significantly. Through-movement waiting areas (TWAs) can be set at the symmetric intersection effectively, which can increase the capacity and short the cycle length furthermore. And the symmetric intersection is Channelized to improve the safety of TWAs. The Binary-Mixed-Integer-Linear-Programming (BMILP) model is employed to formulate the capacity maximization problem and signal cycle length minimization problem of the symmetric intersection. The BMILP model can be solved by standard branch-and-bound algorithms efficiently and outputs the lane allocation, signal timing decisions, and other decisions. Experiments analysis shows that the symmetric intersection with TWAs can increase the capacity and short the signal cycle length.     

A continuous-flow-intersection-lite design and traffic control for oversaturated bottleneck intersections

Oversaturation has become a severe problem for urban intersections, especially the bottleneck intersections that cause queue spillover and network gridlock. Further improvement of oversaturated arterial traffic using traditional mitigation strategies, which aim to improve intersection capacity by merely adjusting signal control parameters, becomes challenging since exiting strategies may (or already) have reached their “theoretical” limits of optimum. Under such circumstance, several novel unconventional intersection designs, including the well-recognized continuous flow intersection (CFI) design, are originated to improve the capacity at bottleneck intersections. However, the requirement of installing extra sub-intersections in a CFI design would increase vehicular stops and, more critically, is unacceptable in tight urban areas with closed spaced intersections. To address these issues, this research proposes a simplified continuous flow intersection (called CFI-Lite) design that is ideal for arterials with short links. It benefits from the CFI concept to enable simultaneous move of left-turn and through traffic at bottleneck intersections, but does not need installation of sub-intersections. Instead, the upstream intersection is utilized to allocate left-turn traffic to the displaced left-turn lane. It is found that the CFI-Lite design performs superiorly to the conventional design and regular CFI design in terms of bottleneck capacity. Pareto capacity improvement for every traffic stream in an arterial system can be achieved under effortless conditions. Case study using data collected at Foothill Blvd in Los Angeles, CA, shows that the new design is beneficial in more than 90% of the 408 studied cycles. The testing also shows that the average improvements of green bandwidths for the synchronized phases are significant.