交通冲突技术在桂林市交叉口安全评价中的应用

文章通过引入交通冲突的概念,以早高峰、晚高峰、平峰三时段的交通冲突量与混合交通当量比值作为交通安全评价的指标,利用灰色理论对桂林市九个典型交叉口进行安全程度的评价。     

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。     

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.     

基于交通冲突技术的高速公路合流区段安全性研究

为研究高速公路合流区段的安全性,本文以四川省境内高速公路为例对典型合流区段的交通冲突特性展开研究。选用PET作为评价指标并将交通冲突划分为3个等级:潜在冲突、轻微冲突、严重冲突。通过建立有序Logistic模型来探索影响冲突严重程度的显著性因素。结果表明:交织区交通流量、冲突车辆的速度差和二次冲突是增加冲突严重性的主要诱因;加速车道长度、规范的标志标线是保护因素;重型车辆比例对冲突严重程度影响呈非线性关系。     

信号交叉口安全评价及时空特性分析

为研究信号交叉口机动车冲突,对机动车驾驶人心理、行为特征进行分析。基于交叉口事故样本的静态数据、交通量和交通冲突数据为动态数据运用FKM聚类法对交叉口安全性进行评估。在此基础上研究交叉口机动车冲突分析时空特性,发现不同交叉口时间、空间冲突特征存在高度相关性和相似性;高峰时段冲突严重度和高峰时段、高峰小时流量存在线性关系并呈反比例关系;机动车冲突在不同空间上的危险度存在差异,其中直行与对向左转冲突危险度最高。     

广西公路项目平交式工程安全评价探讨

文章介绍了公路项目平面交叉口工程安全评价的目的,分析了影响公路项目平面交叉口工程安全的因素,并以广西来马高速马山南互通出口与G210公路平交口项目为工程实例,从平纵线形、视距、交叉口间距、交通工程、施工方案等方面对公路项目平交式工程进行安全评价。     

平面交叉口慢行交通设施安全评价

为了客观评价平交口的慢行交通设施安全状况,从必备性、合理性、完好性三个角度出发,建立平交口慢行交通设施评价指标体系和评价方法,并结合江苏省淮安市枚皋路与承德南路交叉口做了案例分析,评价该交叉口慢行交通交通安全状况。     

四相位信号交叉口的自适应控制研究

基于二流理论,以四相位信号交叉口为研究对象,通过采集交通流数据构建当量长度模型,将计算出的当量排队长度作为信号交叉口自适应控制的依据。最终,进行模糊综合评价,通过选取三个评价指标(车均延误时间、饱和度、排队长度)对某一四相位信号交叉口实施的自适应控制方案前后进行对比,验证此方案的合理性。     

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。     

交叉口自行车交通服务品质评价方法及应用

交叉口是自行车骑行路径的控制节点,是决定骑行感受的重要组成部分。将交叉口自行车交通服务品质分为通过交叉口服务品质和交叉口区域待行服务品质两部分,从骑行者意愿和行为层面分析服务品质的影响要素。采集了上海市杨浦区21个典型交叉口67条进口道的设施特征,并对292名骑行者开展服务品质影响因素问卷调查,确定了评价指标的选取、量化分级和权重划分,采用聚类分析和层次分析等方法构建了交叉口自行车交通服务品质量化评价模型。研究表明:交叉口机动车流量、机动车专用右转车道设置、交叉口穿越距离以及进口道机非隔离形式是影响交叉口自行车交通服务品质的关键因素;其他影响因素还包括进口道宽度、铺面质量和遮荫条件等。最后,应用建立的评价方法,对上海市杨浦区典型骑行路径进行了服务品质评价与对比分析。     

Traffic conflict models to evaluate the safety of signalized intersections at the cycle level

The safety of signalized intersections has often been evaluated at an aggregate level relating collisions to annual traffic volume and the geometric characteristics of the intersection. However, for many safety issues, it is essential to understand how changes in traffic parameters and signal control affect safety at the signal cycle level. This paper develops conflict-based safety performance functions (SPFs) for signalized intersections at the signal cycle level. Traffic video-data was recorded for six signalized intersections located in two cities in Canada. A video analysis procedure is proposed to collect rear-end conflicts and various traffic variables at each signal cycle from the recorded videos. The traffic variables include: traffic volume, maximum queue length, shock wave characteristics (e.g. shock wave speed and shock wave area), and the platoon ratio. The SPFs are developed using the generalized linear models (GLM) approach. The results show that all models have good fit and almost all the explanatory variables are statistically significant leading to better prediction of conflict occurrence beyond what can be expected from the traffic volume only. Furthermore, space-time conflict heat maps are developed to investigate the distribution of the traffic conflicts. The heat maps illustrate graphically the association between rear-end conflicts and various traffic parameters. The developed models can give insight about how changes in the signal cycle design affect the safety of signalized intersections. The overall goal is to use the developed models for the real-time optimization of signalized intersection safety by changing the signal design.     

A programmable calculation procedure for number of traffic conflict points at highway intersections

Traffic movement conflict points at intersections are the points at which traffic movements intersect (including crossing, merging, and diverging). Numbers and distribution of different types of conflict points are used to evaluate intersection access management designs and safety performance. Traditionally, the determination of the numbers of conflict points for different traffic movements is based on manual methods, which causes the difficulty for computerized procedures to evaluate safety performance of different access management designs. Sometimes, a programmable calculation procedure may provide more effective solutions as compared with manual methods. This paper presents a programmable calculation procedure for the determination of the numbers of conflict points, which could be used as a basis for a computerized procedure. Concepts of virtual movement lanes and intersection quadrants are introduced to specify types of intersections, traffic lane configurations, and traffic movement regulations. Calculation models, based on such concepts, for traffic movement conflict points at signalized and unsignalized intersections can be obtained. In support of the procedure, case studies are presented in the paper. The procedure presented in the paper can be programmed into a computer program for the purpose of a computerized evaluation of intersection safety and design performance of different access management or control approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

Developing evasive action‐based indicators for identifying pedestrian conflicts in less organized traffic environments

There has been a growing interest in using surrogate safety measures such as traffic conflicts to analyse road safety from a broader perspective than collision data alone. This growing interest has been aided by recent advances in automated video‐based traffic conflict analysis. The automation enables accurate calculation of various conflict indicators such as time‐to‐collision and post‐encroachment time. These indicators rely on road users getting within specific temporal and spatial proximity from each other and therefore assume that proximity is a surrogate for conflict severity. However, this assumption may not be valid in many driving environments where close interactions between road users are common. The objective of this paper is to investigate the applicability of time proximity conflict indicators for evaluating pedestrian safety in less‐organized traffic environments with a high mix of road users. Several alternative behavioural conflict indicators based on detecting pedestrian evasive actions are recommended to better measure traffic conflicts in such traffic environments. These indicators represent variations in the spatio‐temporal gait parameters (step length, step frequency and walk ratio) immediately before the conflict point. A highly congested shared intersection in Shanghai, China, with frequent pedestrian conflicts is used as a case study. Traffic conflicts are analysed with the use of automated video‐based analysis techniques. The results showed that evasive action‐based indicators have higher potential to identify pedestrian conflicts and measure their severity in high mix less organized traffic environments than time proximity measures such as time‐to‐collision and post‐encroachment time. Copyright © 2016 John Wiley & Sons, Ltd.     

A combined use of microscopic traffic simulation and extreme value methods for traffic safety evaluation

This paper proposes a combined usage of microscopic traffic simulation and Extreme Value Theory (EVT) for safety evaluation. Ten urban intersections in Fengxian District in Shanghai were selected in the study and three calibration strategies were applied to develop simulation models for each intersection: a base strategy with fundamental data input, a semi-calibration strategy adjusting driver behavior parameters based on Measures of Effectiveness (MOE), and a full-calibration strategy altering driver behavior parameters by both MOE and Measures of Safety (MOS). SSAM was used to extract simulated conflict data from vehicle trajectory files from VISSIM and video-based data collection was introduced to assist trained observers to collect field conflict data. EVT-based methods were then employed to model both simulated/field conflict data and derive the Estimated Annual Crash Frequency (EACF), used as Surrogate Safety Measures (SSM). PET was used for EVT measurement for three conflict types: crossing, rear-end, and lane change. EACFs based on three simulation calibration strategies were compared with field-based EACF, conventional SSM based on Traffic Conflict Techniques (TCT), and actual crash frequency, in terms of direct correlation, rank correlation, and prediction accuracy. The results showed that, MOS should be considered during simulation model calibration and EACF based on the full-calibration strategy appeared to be a better choice for simulation-based safety evaluation, compared to other candidate safety measures. In general, the combined usage of microscopic traffic simulation and EVT is a promising tool for safety evaluation.     

Using stop bar detector information to determine turning movement proportions in shared lanes

Turning vehicle volumes at signalized intersections are critical inputs for various transportation studies such as level of service, signal timing, and traffic safety analysis. There are various types of detectors installed at signalized intersections for control and operation. These detectors have the potential of producing volume estimates. However, it is quite a challenge to use such detectors for conducting turning movement counts in shared lanes. The purpose of this paper was to provide three methods to estimate turning movement proportions in shared lanes. These methods are characterized as flow characteristics (FC), volume and queue (VQ) length, and network equilibrium (NE). FC and VQ methods are based on the geometry of an intersection and behavior of drivers. The NE method does not depend on these factors and is purely based on detector counts from the study intersection and the downstream intersection. These methods were tested using regression and genetic programming (GP). It was found that the hourly average error ranged between 4 and 27% using linear regression and 1 to 15% using GP. A general conclusion was that the proposed methods have the potential of being applied to locations where appropriate detectors are installed for obtaining the required data. Copyright © 2016 John Wiley & Sons, Ltd.     

浙江省高速公路交通事故特点及防治措施研究

随着经济的快速发展,高速公路通车里程得到快速增长,道路客、货运量及周转量不断高速发展,但高速公路的交通安全问题已经成为一个重要的研究课题。本文首先分析了浙江省高速公路交通事故的特点,然后运用轨迹交叉论进行交通事故的原因分析,识别浙江省高速公路危险源,最后有针对性地提出了浙江省高速公路交通事故防治措施。