Driver's braking behavior approaching pedestrian crossings: a parametric duration model of the speed reduction times

The driver's braking behavior while approaching zebra crossings under different safety measures (curb extensions, parking restrictions, and advance yield markings) and without treatment (baseline condition) was examined. The speed reduction time was the variable used to describe the driver's behavior. Forty‐two drivers drove a driving simulator on an urban scenario in which the baseline condition and the safety measures were implemented. The speed reduction time was modeled with a parametric duration model to compare the effects on driver's braking behavior of vehicle dynamic variables and different countermeasures. The parametric accelerated failure time duration model with a Weibull distribution identified that the vehicle dynamic variables and only the countermeasure curb extensions affected, in a statistically significant way, the driver's speed reduction time in response to a pedestrian crossing. This result shows that the driver, because of the improved visibility of the pedestrian allowed by the curb extensions, was able to receive a clear information and better to adapt his approaching speed to yield to the pedestrian, avoiding abrupt maneuvers. This also means a reduction of likelihood of rear‐end collision due to less aggressive braking. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of intersection field of view on emergent collision avoidance performance at unsignalized intersections: analysis based on driving simulator experiments

Proper intersection sight distance can effectively lower the possibility of intersection accidents. American Association of State Highway and Transportation Officials (2011) provide a series of recommended dimensions of intersection sight triangles for uncontrolled and stop/yield‐controlled intersections. However, in reality, although the actual intersection design for unsignalized intersections satisfies the requirements of sight distance and clear sight triangle in American Association of State Highway and Transportation Officials' guideline, there are still a large number of crashes occurring at unsignalized intersections for drivers running stop/yield signs or failing to slow down. This paper presents a driving simulator study on pre‐crash at intersections under three intersection field of view (IFOV) conditions. The aim was to explore whether better IFOVs at unsignalized intersections improve their emergent collision avoidance performance under an assumption of valid intersection sight distance design. The experimental results show drivers' ability to identify potential hazards to be significantly affected by their IFOVs. As drivers' IFOV improved, drivers were more likely to choose braking actions to avoid collisions. Better IFOVs were also associated with significant increases in brake time to intersection and significant reductions in deceleration rate and crash rate, thus leading to a lower risk of traffic crash involvement. The results indicate that providing a better IFOV for drivers at intersections should be encouraged in practical applications in order to improve drivers' crash avoidance capabilities. Copyright © 2016 John Wiley & Sons, Ltd.     

沥青混合料破坏阶段的黏弹性行为

采用基于连续破坏力学和功势原理的模型对沥青混合料破坏阶段的黏弹性行为进行研究.该模型中利用虚应变来描述沥青混合料的时间依赖性,利用破坏参数和虚劲度模量的关系描述沥青混合料的破坏特性.通过不同条件下的复数模量试验确定了沥青混合料的线黏弹性力学参数,进行了不同条件下的恒应变率压缩试验来确定沥青混合料的破坏特性.确定了破坏参数、应力的勒贝格范数和虚劲度模量之间的关系,进而用线性分段法计算了沥青混合料的黏弹性应变.利用该模型对不同条件下的恒应变率压缩试验结果进行了分析.结果表明:预测值和实测值吻合良好.     

上海世博游客的交通与游憩行为融合对策

为应对2010年上海世博会吸引大量游客及对上海市造成的交通压力,对游客的交通行为和游憩行为进行研究。首先综合上海市及以往世博会举办城市的交通数据,对2010年世博游客基本特征进行分析及预测。从交通的角度,根据不同交通方式的优势范围划分4个世博交通服务圈层,进而分析世博游客的流向分布及其与日常交通流叠加的特点。从游憩的角度,探讨游客的游憩行为及旅游路线。最终指出,交通尤其是公共交通各个环节与游憩的融合很重要。提出降低观光隧道票价、将水上巴士变成流动的世博会场馆等建议。     

高强钢-混凝土组合梁受力性能分析

为研究高强钢-混凝土组合梁中结构几何参数及材料强度对组合梁受力性能的影响,建立了14组构件在跨中两点对称荷载作用下的有限元数值模型,对其受力性能进行了分析。分析结果表明:在承载能力极限状态下,钢梁的贡献占竖向抗剪强度约77.0%;在弹性与塑性阶段,不同材料强度的组合梁的跨中最小与最大挠度比值分别为79.5%和28.0%;在塑性状态下,不同混凝土板横向配筋率和宽度的组合梁的跨中最小与最大挠度比值分别为62.1%和53.3%,不同材料强度、混凝土板宽度、横向配筋率和厚度的组合梁的最小与最大纵向滑移量比值分别为25.0%、41.9%、63.2%、70.7%。可见,提高钢梁强度或增大钢梁尺寸可显著提高组合梁竖向抗剪能力;材料强度对组合梁弹性工作阶段的跨中挠度影响较小,混凝土板横向配筋率及其宽度对塑性状态下跨中挠度有较大影响;弹性工作阶段材料与几何参数对组合面滑移的影响不明显,塑性状态下材料强度、混凝土板宽度、横向配筋率及厚度对纵向滑移影响较大。     

非机动车骑行行为实验研究

基于交通信息负荷量和交通信息变化的非机动车骑行过程,分析了骑行行为的安全性．针对不同的交通信息负荷量下非机动车骑行者的骑行行为,从骑行的安全感和舒适度出发,借助交通行为分析理论,设计了非机动车行车实验的研究方法,通过对比实验研究,分析了非机动车的速度和加速度特点,并根据自行车速度不稳定、波动频率高,而电动自行车速度相对稳定,但速度高、加速度大的特点,得出电动自行车安全性差的结论,验证了实验方法的可行性与合理性．     

基于优势关系粗糙集的驾驶行为研究

在分析驾驶行为影响因素的基础上,提出了用粗糙集理论求解驾驶员的轨迹决策问题的方法.将驾驶员模糊多目标轨迹决策模型看成是一个具有偏好信息的多属性决策问题,用优势关系代替不可分辨关系,并通过优势属性集来推理决策规则,从而确定各预期轨迹点的排序.     

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在城市生活中,相对于同年龄层男性的对比群体,女性出行行为的各项统计指标具有显著差异。本文基于2005年北京市居民出行调查的样本数据,比较分析了女性的出行行为在出行率、出行时耗、出行目的及出行方式等方面的特征。进一步地,引入了出行链的概念,利用非集计理论和方法,构建了女性早通勤出行链选择行为模型,从源头上分析影响女性个体出行链选择行为的10个重要因素;并利用模型估计所得的参数计算事件发生比,量化了各个影响因素对女性出行链选择行为的影响程度。研究结果表明：女性老年人的出行率远低于男性老年人;女性在购物和社会生活等出行目的上的出行比例明显高于男性,且平均出行时耗受家庭结构因素的制约较为突出;女性出行采用的主要交通方式为步行,且远高于男性的相应值;年龄、是否持有驾照、家庭月收入、家庭交通工具拥有情况是影响女性出行链选择行为的主导因素。     

Modeling the flexural carrying capacity of corroded RC beam

Considering the change of bond strength between corroded steel and concrete, flexural carrying ca-pacity of corroded reinforced concrete (RC) beam was calculated. On the basis of the condition of equilibriumof forces and compatibility of deformations for the whole beam, a model for the prediction of flexural carryingcapacity of the corroded RC beam was proposed. Comparison of the model's predictions with the experimentalresults published in the literature shows the practicality of the proposed method.     

三塔悬索桥关键设计参数对其结构行为的影响

泰州长江公路大桥初步设计推荐2×1 080 m的三塔双主跨悬索桥方案。利用有限元模型对其关键设计参数如矢跨比、中塔高度、加劲梁高度,以及支承体系等对其结构行为的影响进行了研究,研究成果均在泰州长江公路大桥初步设计中采用。