Increasing the Capacity of the Intersection Downstream of the Freeway Off‐Ramp Using Presignals

High volume from urban freeway off‐ramps coupled with extensive traffic weaving and limited capacity at downstream intersections create major bottlenecks in urban road networks. This article presents an integrated design model to eliminate traffic weaving and to maximize the section's overall capacity by using the presignal and sorting area concept. The selection of movements controlled by the presignal, the layout of the section, and the signal timing are optimized in a uniform framework by a mixed‐integer nonlinear program model. The mathematical model was linearized and solved using the standard branch‐and‐bound technique. Extensive numerical analysis and a case study validate the effectiveness of the proposed integrated model in improving capacity with the comparison of conventional design under various geometric configuration and traffic demand pattern scenarios. The proposed model has promising application at locations where the queuing space is long enough and the number of exit lanes is enough to receive the traffic stream from the sorting area.     

Robust Optimal Lane Allocation for Isolated Intersections

Lane allocation including approach and exit lane numbers and lane markings of approach lanes plays an important role in improving the capacity of an intersection. Conventional approaches for optimizing lane allocation often ignore fluctuations in traffic demand (TD). This article presents a stochastic model for robust optimal lane allocation of an isolated intersection under stochastic traffic conditions. This model is built in three steps. In the first step, an enhanced lane‐based model in the form of a binary mixed‐integer nonlinear program is proposed to optimize lane allocation and traffic signals for both vehicles and pedestrians in a unified framework under deterministic traffic conditions. In the second step, a two‐level stochastic model is developed to obtain a robust lane allocation that is less sensitive to traffic flow fluctuations considering the flexibility of traffic signals. In the third step, the two‐level model is further transformed into a TD‐based stochastic model in a two‐phase form to reduce the solution dimension for efficient computation. A TD‐based genetic algorithm procedure is presented for solvability. Numerical studies are conducted to validate the model formulations and solution algorithms.     

Modeling adaptive platoon and reservation-based intersection control for connected and autonomous vehicles employing deep reinforcement learning

As a cutting-edge strategy to reduce travel delay and fuel consumption, platooning of connected and autonomous vehicles (CAVs) at signal-free intersections has become increasingly popular in academia. However, when determining optimal platoon size, few studies have attempted to comprehensively consider the relations between the size of a CAV platoon and traffic conditions around an intersection. To this end, this study develops an adaptive platoon-based autonomous intersection control model, named INTEL-PLT, which adopts deep reinforcement learning technique to realize the optimization of multiple dynamic objectives (e.g., efficiency, fairness, and energy saving). The framework of INTEL-PLT has a two-level structure: The first level employs a reservation-based policy integrated with a nonconflicting lane selection mechanism to determine the lanes’ releasing priorities; and the second level uses a deep Q-network algorithm to identify the optimal platoon size based on real-time traffic conditions (e.g., traffic density, vehicle movement, etc.) of an intersection. The model is validated and examined on the simulator Simulation of Urban Mobility. It is found that the proposed model exhibits superior performances on both travel efficiency and fuel conservation as compared with state-of-the-art methods in three typical traffic conditions. Moreover, several in-depth insights learned from the simulations are provided in this paper, which could better explain the relation between platoon size and traffic condition.     

Wireless charging utility maximization and intersection control delay minimization framework for electric vehicles

This study presents the Wireless Charging Utility Maximization (WCUM) framework, which aims to maximize the utility of Wireless Charging Units (WCUs) for electric vehicle (EV) charging through the optimal WCU deployment at signalized intersections. Furthermore, the framework aims to minimize the control delay at all signalized intersections of the network. The framework consists of a two‐step optimization formulation, a dynamic traffic assignment model to calculate the user equilibrium, a traffic microsimulator to formulate the objective functions, and a global Mixed Integer Non‐Linear Programming (MINLP) optimization solver. An optimization problem is formulated for each intersection, and another for the entire network. The performance of the WCUM framework is tested using the Sioux Falls network. We perform a comparative study of 12 global MINLP solvers with a case study. Based on solution quality and computation time, we choose the Couenne solver for this framework.     

A Schematic Urban Street Network-Display Algorithm

The link-node network is the most commonly used model for representing a large-scale urban street system. It is easy to formulate a mathematical model which describes the complicated spatial and temporal urban-street-related problems on such a simplified network representation. However, recently developed microscopic network traffic models contain important details which cannot be depicted on the link-node diagram. This paper describes a computer-graphics algorithm which can generate a lane-detailed schematic urban street network display. The algorithm is very comprehensive, and it can accommodate various types of urban street configurations. The regular four-approach, right-angle intersection can be displayed most accurately. However, intersections with more or less than four approaches and/or links intersecting at an angle other than 90-deg can be generated satisfactorily. One-way streets intersecting two-way or one-way streets can also be depicted. Furthermore, roadways where the number of lanes changes (for example, from two lanes to three lanes, or from two lanes to one lane) can also be plotted. The overall quality of the display generated by this algorithm is satisfactory. The required input data is relatively simple, although the time associated with the input data preparation is short. In addition, applications using this algorithm are also discussed.     

平面交叉口通行能力的影响因素

主要从道路和交通条件对平面交叉口的交通运行状况进行了分析,提出了影响平面交叉口通行能力的几个影响因素,指出应考虑空间上的分离及时间上的分流并兼顾其他因素,从根本上提高平面交叉口的通行能力。     

考虑交叉口特性的疏散交通路线研究

疏散是应急管理中的重要措施,在应急计划中有必要制定合理的疏散路线以确保疏散车辆尽快到达终点。以往有关最佳疏散交通路线的研究没有考虑交叉口延误和通行能力等因素,若疏散路线经过城市内拥挤路段,忽略交叉口的这些特性会导致结果不尽合理。将交叉口分方向延误和通行能力作为节点权重,建立了点权交通网络,通过在点权网络中求解最小费用流来优化事故地点至安全地点的最佳疏散交通路线及相应的疏散流量,设计了一种最小费用路算法求解该点权网络中的最小费用流。最后以一个数值算例说明了方法的应用,并对考虑和忽略交叉口特性2种情况下得出的路线进行了对比。结果表明该方法能很好地兼顾路网特点和疏散路线优化的要求;若执行忽略交叉口特性的疏散路线方案,极易造成交叉口的拥堵,延长车辆的走行时间。     

集散一级公路平面交叉口交通安全对策研究

从工程设计的角度对国内集散一级公路平面交叉口存在的安全问题进行了分析研究,并针对这些问题提出了相应对策和改善公路平面交叉口交通安全、提高通行能力的公路平交路口安全设计方法,以保障集散一级公路交叉口的交通安全和畅通。     

A spatiotemporal control method at isolated intersections under mixed-autonomy traffic conditions

With the introduction of connected and automated vehicles (CAVs), the integrated control of traffic signals, lane assignments, and vehicle trajectories becomes feasible, offering notable benefits for enhancing intersection operations. However, during the prolonged transition to an entirely CAV environment, how to fully leverage the advantage of CAVs while considering the characteristics of human-driven vehicles remains a huge challenge. To address this challenge, this paper proposes a joint optimization method for spatiotemporal resources at isolated intersections under mixed-autonomy traffic conditions. Initially, the lane assignment optimization problem is modeled as a mixed integer linear program model to maximize the reserve capacity. Subsequently, the signal-vehicle coupled control is formulated as a dynamic programming model with the objective of reducing vehicle travel time. Additionally, criteria are established to assess the need for re-optimizing lane assignments. Simulations validate the superiority of the proposed control method over adaptive control in terms of traffic efficiency and intersection capacity amid substantial traffic demand fluctuations. Sensitivity analyses reveal that the proposed control method can yield higher benefits under medium traffic demand levels. Furthermore, the proposed algorithm exhibits no significant sensitivity to the CAV market adoption rate, suggesting its applicability throughout the CAV adoption process.     

环形交叉口信号灯联动设计初探

将环行交叉口及其相邻受信号灯控制的平面交叉口组合在一起 ,通过信号灯联动控制设计实现由不同方向来的车辆在同一信号灯周期不同时段错位通过环行交叉口 ,从而提高环行交叉口通行能力。     

道路平面交叉口次路远引几何参数设置及通行效率研究

次要车流的左转和直行对交叉口车辆运行影响较大,特别是主路交通流量较大时尤为明显,通过次要道路车流远引的方式可以减少交叉口车辆冲突,有利于提高交叉口运行效率。分析了平面交叉口次路远引适用条件与车流组织方法,以延误最小为目标,构建了远引回转车流掉头位置、远引车辆掉头排队车道长度、远引掉头处开口长度与宽度等关键几何参数计算模型,提出了次路远引交叉口延误和通行能力等计算方法。结合实例验证了上述方法的可行性,仿真显示,在一定条件下平面交叉口次路远引可有效减少信号相位数和车辆平均延误,表明了平面交叉口次路远引的交通组织方法对优化城市道路交叉口设计有较好的应用价值。     

南京江东路道路改造设计理念的综合应用

结合南京市江东路道路改造实例,通过横断面设计、交叉口渠化、交通岛设置、公交专用道、人行横道、主线绿波交通、绿化景观等设计理念的综合应用,极大地提高了城市道路的服务水平。道路预计通行能力由2103pcu/h提高到3450pcu/h;公交运营速度增加;大大提高了交通安全性;良好的景观效果得到了一致好评。     

平面交叉口交通控制与管理不安全因素分析

在现场调查分析交通标志、标线、信号设置存在问题,视距不良、交叉路口交通组织和渠化不当等的基础上,总结了公路平面交叉口在交通控制与管理方面常见的9个不安全因素。运用事故折减系数(CRF)统计数据分析了不安全因素引起事故的可能性,采用汽车碰撞理论分析与专家调查结合的方法,进行各事故类型的严重性分析,进一步确定了各不安全因素的危险性指数,得到其危险性排序,为交叉口安全诊断和安全保障研究提供了依据。     

Modeling urban intersection form: Measurements,patterns, and distributions

Intersections appear where one street crosses another, acting as fundamental nodes embedded in the network of urban public space. Though discussed in configurational and perceptive studies, limited attention has been paid to the morphological aspects of intersections. This study proposes and tested a new approach to modeling the urban intersection form. First, effective cylinder was introduced to define the related space for each intersection based on its scale. Second, a set of morphological indicators were presented to measure the physical properties of the intersection form. Third, the affinity propagation algorithm was used to examine the patterns of intersection form. Using the Old City of Nanjing, China as the study area, 844 intersections were analyzed to test this new method. As a result, we were able to classify the intersections into eight types. This study shows that the intersection can be modelled as a volumetric and integral spatial unit of urban form, which may demand more attention from urban designers and architects in the future for shaping the built environment. The quantitative nature of our method could also open more possibilities for intersection-based studies.     

A comparative analysis of cyclists’ paths through shared space and non-shared intersections in Coventry,England

This paper investigates the impact that road design may have on how cyclists ride through intersections. Using video observations of two intersections in Coventry, England, one shared and one non-treatment, an analysis of the paths taken by cyclists examines the variation in the paths ridden through the non-treatment intersection as compared to the shared space intersection. The results of this comparative analysis indicate that a significant proportion of observed cyclists ride similarly through both shared and non-treatment intersections. These findings indicate that shared space designs may not influence cyclists as the design theory itself states.     

平面交叉口新型安全措施

平面交叉口是交通事故的多发地。其原因有多种;其中交叉口在交通设施及设置设计等方面存在的不足,是原因之一。因此,对平面交叉口进行改进,提高交叉口的安全性,具有重要的实用价值和意义。目前,国内外对交叉口安全进行了大量研究,分别从交叉口安全效果评价、事故空间分析,机动车、行人、非机动车的交通控制设施,交叉口几何设计等几个方面入手,提出了一些新型的交叉口安全改善措施。经实践检验,这些措施对交叉口安全水平的提高有很好的促进作用。     

行人影响下的信号交叉口通行能力研究

为量化行人交通对信号交叉口通行能力的影响,分析了行人-机动车冲突点处的行人行为特征和人车运行规律,并描述了行人成群到达的现象。在此基础上,利用车队分析法建立冲突点车辆通行能力模型,并且利用实测数据标定模型参数,为计算行人影响下的信号交叉口通行能力提供了分析依据。模型计算的冲突车流通行能力很大程度取决于有效绿灯时间内冲突点处人车冲突的平均次数。模型计算通行能力总体上低于HCM 2000方法,结果随行人流量增加而呈现的下降趋势渐趋平缓。模型建立在冲突点运行规律基础之上,具有较广泛的适应性。研究为混合交通条件下信号交叉口配时设计与交通管理提供了理论基础。     

Two‐Dimensional Simulation of Turning Behavior in Potential Conflict Area of Mixed‐Flow Intersections

The potential conflict area of intersection is the space where conflicting traffic flows pass through in the same signal phase. At this area, turning vehicles interact with most traffic flows, which introduce complex features including variation of trajectories and shared‐priority phenomenon. The traditional one‐dimensional simulation oversimplifies these features with lane‐based assumption. This study integrates the modified social force model with behavior decision and movement constraints to reproduce the two‐dimensional turning process. The method is framed into a three‐layered mathematical model. First, the decision layer dynamically makes decision for turning patterns. Then the operation layer uses the modified social force model to initially generate vehicle movements. Finally, the constraint layer modifies the vehicular motion with vehicle dynamics constraints, boundary of intersection and the collision avoidance rule. The proposed model is validated using trajectories of left‐turn vehicles at a real‐world mixed‐flow intersection with nonprotected signal phases, resulting in a more realistic simulation than previous methods. The distributions of decision points and travel time in simulation are compared with the empirical data in statistics. Moreover, the spatial distribution of simulated trajectories is also satisfactory.     

天津某环岛交叉口的改建方案

在天津黄海路与第二大街环岛交叉口改建工程中,根据交通状况和限制条件,提出了几种提高交叉口通行能力的方法。经综合比较,推荐采用不破坏环岛形式并通过信号灯控制的交叉口设计方案,达到了提高交叉口通行能力的目的。     

Rolling-horizon–based strategy of fully cooperative traffic under signalized intersections

Dedicated left-turn lanes are traditionally used at intersections. This practice may not be optimal where heavy traffic exists from multiple directions. As is well known, the capacity can be increased if vehicles are grouped in the same direction in advance, but the additional infrastructure is usually needed, such as presignal systems. Fortunately, under the development of connected and automated vehicle (CAV) technology, the presignal system can be achieved by coordinating vehicles directly. To this end, we establish a modeling framework and management strategies for pure CAV traffic to achieve direction-based grouping. A rolling time-horizon–based sorting strategy is developed to achieve real-time coordination under uncertain vehicle arrivals. A series of numerical experiments have shown that the improvement of the proposed sorting strategy is significant and robust compared with traditional dedicated left-turn lane intersections without coordination, especially when the traffic is busy.