事故车辆影响下的城市道路交通仿真研究

为研究事故车辆影响下城市道路交通的特征，构建考虑车辆抢道行为的元胞自动机交通流模型，研究给定冲突区域长度下不同进车率和不同事故持续时间对城市道路交通流的影响。研究结果表明:事故车辆会诱发交通瓶颈，对城市交通产生显著干扰并形成拥堵带，且拥堵带向事故车辆上游传递。不同事故持续时间下交通流演化存在差异，道路平均车流量、车流平均密度随着事故持续时间的增加而增加，车辆平均速度随之减小。当道路中车辆较少（pin=0.3）且事故持续时间达到15 min时，交通处于严重拥堵状态；当道路中车辆较多（pin=0.5）、事故持续时间达到5 min时，交通即处于严重拥堵状态。研究结果可为优化城市交通事故处理机制提供依据。     

旅游景区的低碳交通模式研究

景区内部交通构成旅游景区碳排放的主体，创建低碳旅游景区必然要走低碳交通之路。旅游景区的低碳交通建设是一个系统工程。从低碳景区创建角度出发，对景区内几种典型交通方式的碳排放情况进行定量分析和初步比较，从交通工具的选择与改进、交通站点的合理设置、景区道路的科学规划、运营管理的技术引入等方面构建旅游景区的低碳交通模式，为相关景区选择低碳化的交通方式提供依据。     

机动车不同速度下外噪声变化与衰减关系研究

通过在机动车测试场进行单辆机动车行驶状况的实验,研究机动车车型大小、行驶速度快慢与噪声量大小的关系,同时研究不同距离下机动车行驶外噪声的衰减规律。数据结果显示,测试条件下,噪声量随着速度提升而增加,呈线性关系或对数关系;相同速度下,大型车的噪声量比小型车的高8.1～11.0dB;在一定距离范围内,距离每增加3.5m,机动车噪声量将衰减2.2～3.0dB。     

石家庄市道路交通环境NO_x污染水平及ARMA模型预测

选择石家庄市区代表性路段作为研究对象,对其交通环境空气中NOx的污染水平进行现状监测。基于Matlab软件建立拟合模型,对下一时期的NOx污染趋势进行预测。结果表明,石家庄市交通环境中NOx小时浓度介于0.047~0.237 mg/m3之间,呈早晚高,且下午明显低于上午的日变化规律;NOx日均浓度介于0.076~0.211 mg/m3之间,其浓度与车流量呈明显的正相关性。利用matlab软件建立的ARMA模型能够较好地预测道路交通环境空气中NOx的浓度变化趋势。     

Evaluation of countermeasures for red light running by traffic simulator–based surrogate safety measures

Objective: The conflicts among motorists entering a signalized intersection with the red light indication have become a national safety issue. Because of its sensitivity, efforts have been made to investigate the possible causes and effectiveness of countermeasures using comparison sites and/or before-and-after studies. Nevertheless, these approaches are ineffective when comparison sites cannot be found, or crash data sets are not readily available or not reliable for statistical analysis. Considering the random nature of red light running (RLR) crashes, an inventive approach regardless of data availability is necessary to evaluate the effectiveness of each countermeasure face to face.

Method: The aims of this research are to (1) review erstwhile literature related to red light running and traffic safety models; (2) propose a practical methodology for evaluation of RLR countermeasures with a microscopic traffic simulation model and surrogate safety assessment model (SSAM); (3) apply the proposed methodology to actual signalized intersection in Virginia, with the most prevalent scenarios—increasing the yellow signal interval duration, installing an advance warning sign, and an RLR camera; and (4) analyze the relative effectiveness by RLR frequency and the number of conflicts (rear-end and crossing).

Results: All scenarios show a reduction in RLR frequency (?7.8, ?45.5, and ?52.4%, respectively), but only increasing the yellow signal interval duration results in a reduced total number of conflicts (?11.3%; a surrogate safety measure of possible RLR-related crashes). An RLR camera makes the greatest reduction (?60.9%) in crossing conflicts (a surrogate safety measure of possible angle crashes), whereas increasing the yellow signal interval duration results in only a 12.8% reduction of rear-end conflicts (a surrogate safety measure of possible rear-end crash).

Conclusions: Although increasing the yellow signal interval duration is advantageous because this reduces the total conflicts (a possibility of total RLR-related crashes), each countermeasure shows different effects by RLR-related conflict types that can be referred to when making a decision. Given that each intersection has different RLR crash issues, evaluated countermeasures are directly applicable to enhance the cost and time effectiveness, according to the situation of the target intersection. In addition, the proposed methodology is replicable at any site that has a dearth of crash data and/or comparison sites in order to test any other countermeasures (both engineering and enforcement countermeasures) for RLR crashes.     

An analysis of cyclists’ speed at combined pedestrian and cycle paths

Abstract

Objective: In Sweden, cyclists, pedestrians, and moped riders share the space on combined pedestrian and cycle paths, and their speeds may differ greatly. Both actual speed and speed differences can potentially influence the number of accidents on the shared paths. As a starting point, this article studies the speed component and how cyclists’ speed varies at pedestrian and cycle paths depending on the day, week, and year; road user composition; and road design.

Methods: Three data sources were used: Existing measurements of cycle speed and flow in 3 different Swedish municipalities, Eskilstuna (1 site, January–December 2015), Linköping (6 sites, 4?weeks in September–October 2015), and Stockholm (10 sites, 1–5?days in August–September 2015); complementary measurements of cycle speed and flow in Linköping (4 sites, 1–10?days in August–September 2016) and Stockholm (1 site, only part of 2?days in August 2016) were also conducted within the project, in addition to roadside observations of bicycle types at the 5 new sites.

Results: The average speed of cyclists on the paths varied between 12.5 and 26.5?km/h. As expected, the lower average speeds were found in uphill directions, near intersections, and on paths with high pedestrian flows. The higher speeds were found in downhill directions and on commuter routes. In all, 70%–95% of road users observed on pedestrian and cycle paths were cyclists, and 5%–30% were pedestrians. The most common type of bicycle was a comfort bike, followed by a trekking bike. Electric-assisted bicycles and racer bikes occurred at all sites, with proportions of 1%–10% and 1%–15%, respectively. The 2 sites with the highest proportion of electric-assisted bicycles and racer bicycles also had the highest average speeds. The differences in average speed throughout the day, week, and year could only be assessed at one of the sites. Only small differences were found, with the most noticeable being that the average speed was lower in January and February (13.8?km/h) compared to the rest of the year (15.3–16.1?km/h). The average speed was also lower during daytime (14.7?km/h) than during other parts of the day (15.4–15.8?km/h).

Conclusions: The relationship between bicycle type and measured speed was not entirely clear, but the results suggest that paths with higher proportions of electric and racer bicycles have higher average speeds. There also appears to be a connection between average speed and the width of the distribution; that is, the higher the average speed, the wider the speed distribution. More research is needed on how speed levels and speed variance affect accident risk.     

Effects of logging on roadless space in intact forest landscapes of the Congo Basin

Forest degradation in the tropics is often associated with roads built for selective logging. The protection of intact forest landscapes (IFL) that are not accessible by roads is high on the biodiversity conservation agenda and a challenge for logging concessions certified by the Forest Stewardship Council (FSC). A frequently advocated conservation objective is to maximize the retention of roadless space, a concept that is based on distance to the nearest road from any point. We developed a novel use of the empty‐space function – a general statistical tool based on stochastic geometry and random sets theory – to calculate roadless space in a part of the Congo Basin where road networks have been expanding rapidly. We compared the temporal development of roadless space in certified and uncertified logging concessions inside and outside areas declared IFL in 2000. Inside IFLs, road‐network expansion led to a decrease in roadless space by more than half from 1999 to 2007. After 2007, loss leveled out in most areas to close to 0 due to an equilibrium between newly built roads and abandoned roads that became revegetated. However, concessions in IFL certified by FSC since around 2007 continuously lost roadless space and reached a level comparable to all other concessions. Only national parks remained mostly roadless. We recommend that forest‐management policies make the preservation of large connected forest areas a top priority by effectively monitoring – and limiting – the occupation of space by roads that are permanently accessible.     

快速高架复合道路近场交通噪声垂向分布

采用Cadna/A环境噪声模拟软件建立了高架复合道路的基本模型,根据6种基本模拟情况进行了声场模拟,并把模拟结果与实测结果进行对比分析。结果表明,高架道路结构本身对地面道路、高架道路分别形成的声场有明显的遮挡作用,但对高架复合道路所形成的声场遮挡作用不明显;对于高架复合道路垂向声场,在低层段地面道路的影响大于高架道路,而在高层段高架道路的影响起决定作用;高架复合道路较地面道路的垂向声场最大值增加2.5 dB(A),位置上移6m;在高架道路上设置声屏障有一定降噪效果,但在高架复合道路的上层设置声屏障降噪效果不理想。     

Measurement of Particulate Bound Mercury,Gaseous Elemental Mercury,and Reactive Gaseous Mercury Concentrations by Using an Ambient Air Mercury Collection System

In this investigation, the concentrations of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate bound mercury (PBM) in ambient air were measured at the Hung Kuang (traffic) sampling site during September 27 to October 6, 2014. An ambient air mercury collection system (AAMCS) was utilized to measure simultaneously PBM, GEM, and RGM concentrations in ambient air. The results thus obtained demonstrate that the mean concentrations of PBM, GEM, and RGM were 38.57 ± 11.4 (pg/m³), 17.67 ± 5.56 (ng/m³) and 10.78 ± 2.8 (pg/m³), respectively, at this traffic-sampling site. The mean GEM/PBM and GEM/RGM concentration ratios were 458 and 1639, respectively. The results obtained herein demonstrate that AAMCS can be utilized to collect three phases of mercury simultaneously. The mean PBM, GEM, and RGM concentrations herein were compared with others found in Asia, America, Europe and Antarctica. The mean PBM, GEM, and RGM concentrations were found to be lowest in Asia and Antarctica. The mean PBM concentration in Europe was approximately eight times that in this investigation. The mean GEM and RGM concentrations in this study were 1.21 and 170 times those found in the United States.     

浅析美国和澳大利亚及新加坡道路交通噪声管理与监测

简要介绍了美国、澳大利亚及新加坡在道路交通噪声控制管理与监测技术方面的现状,分析了其经验和特点,结合我国道路交通噪声监测与评价现状提出了相应的建议。