Performance measure for reliable travel time of emergency vehicles

Travel time is very critical for emergency response and emergency vehicle (EV) operations. Compared to ordinary vehicles (OVs), EVs are permitted to break conventional road rules to reach the destination within shorter time. However, very few previous studies address the travel time performance of EVs. This study obtained nearly 4-year EV travel time data in Northern Virginia (NOVA) region using 76,000 preemption records at signalized intersections. First, the special characteristics of EV travel time are explored in mean, median, standard deviation and also the distribution, which display largely different characteristics from that of OVs in previous studies. Second, a utility-based model is proposed to quantify the travel time performance of EVs. Third, this paper further investigates two important components of the utility model: benchmark travel time and standardized travel time. The mode of the distribution is chosen as benchmark travel time, and its nonlinear decreasing relationship with the link length is revealed. At the same time, the distribution of standardized travel time is fitted with different candidate distributions and Inv. Gaussian distribution is proved to be the most suitable one. Finally, to validate the proposed model, we implement the model in case studies to estimate link and route travel time performance. The results of route comparisons also show that the proposed model can support EV route choice and eventually improve EV service and operations.     

Analysis of plug-in hybrid electric vehicles’ utility factors using GPS-based longitudinal travel data

The benefit of using a PHEV comes from its ability to substitute gasoline with electricity in operation. Defined as the proportion of distance traveled in the electric mode, the utility factor (UF) depends mostly on the battery capacity, but also on many other factors, such as travel pattern and recharging pattern. Conventionally, the UFs are calculated based on the daily vehicle miles traveled (DVMT) by assuming motorists leave home in the morning with a full battery, and no charge occurs before returning home in the evening. Such an assumption, however, ignores the impact of the heterogeneity in both travel and charging behavior, such as going back home more than once in a day, the impact of available charging time, and the price of gasoline and electricity. Moreover, the conventional UFs are based on the National Household Travel Survey (NHTS) data, which are one-day travel data of each sample vehicle. A motorist’s daily travel distance variation is ignored. This paper employs the GPS-based longitudinal travel data (covering 3–18 months) collected from 403 vehicles in the Seattle metropolitan area to investigate how such travel and charging behavior affects UFs. To do this, for each vehicle, we organized trips to a series of home and work related tours. The UFs based on the DVMT are found close to those based on home-to-home tours. On the other hand, it is seen that the workplace charge opportunities significantly increase UFs if the CD range is no more than 40 miles.     

关于城市道路隧道线形设计的几点体会

城市道路隧道线形设计是一个综合性课题,与地形、地貌、工程地质、水文地质、社会人文和环境等多方面因素密切相关。它需要设计者在满足设计规范的前提下,结合隧道轴线、埋深、洞口位置及洞外接线、施工场地布置、出渣处理、工期长度、营运养护等综合考虑,进行多方案比较,只有这样才能把城市道路隧道的线形设计得更为合理。     

基于选择方案抽样调查的城市群低频率出行行为研究

为分析城市群内低频率城际出行行为,对长三角城市群内上海与其他城市间的城际出行进行选择方案抽样调查,基于城际出行行为调查数据建立出行方式选择的多项Logit(MNL)模型；选择方案抽样调查数据与随机抽样调查数据存在方案分层结构偏差和因素重视度偏差,故引入反转因子(IPW),分别用外源性样本极大似然估计(ESMLE)简单修正法和加权外源性样本极大似然估计(WESMLE)法对MNL模型进行修正.结果表明:未修正模型及2种修正法下的模型命中率分别为57％,75％和84％；WESMLE修正后的模型能基本满足建模精度要求；城市群内低频率城际出行行为受出行时间、费用及个人属性等因素影响,同时,也表现出一定程度的随机性和随意性.     

区位对高铁车站周边地区开发的影响

高铁车站选址需要综合考虑技术、经济以及空间等诸多因素,国内已有研究缺乏针对新建高铁线路边缘化的选址及其对车站周边地区开发影响的定量分析。以京沪和武广高铁沿线城市的38个高铁车站及其周边地区发展状况为研究对象,探索高铁车站与城市中心的距离这一关键因素对高铁车站周边地区开发的影响机制。通过构建距离指数,系统分析不同区位高铁车站周边地区的开发特征,并通过聚类分析,得到车站周边地区开发规模与城市规模、距离指数的关系。结果表明,城市规模越大、距离指数越小,则开发量越大;在22个有开发车站中,距离指数较低(0.5~1.0)的车站周边地区开发效果最为显著;相对大、中开发类车站,小开发类和无开发类车站周边地区的开发情况对于城市规模和距离指数的变化更加敏感。     

上海市大型居住社区居民职住分离情况研究

采用数理统计方法,选择上海市大型居住社区为研究对象,结合大量的实地问卷调查数据,系统地分析上海周边大型居住社区职住分离情况.采用聚类分析方法对大型居住社区居民通勤时间、出行方式选择进行了统计分析,分析发现大型居住社区居民出门时间早于上海市平均时间、居民对公交的依赖性非常强、助动车使用比例较高,这表明大型居住社区公交配套设施之间的衔接不到位,存在站点距离过长和线路不对称等情况.最后通过多个大型居住社区样本之间的比较,找出影响大型居住社区居民职住分离现象的因素,结合实际情况,给出相应改善职住分离现象的建议.     

GIS-based transit trip allocation methods converting stop-level boarding and alighting trips into TAZ trips

ABSTRACT

This study introduces a framework to improve the utilization of new data sources such as automated vehicle location (AVL) and automated passenger counting (APC) systems in transit ridership forecasting models. The direct application of AVL/APC data to travel forecasting requires an important intermediary step that links stops and activities – boarding and alighting – to the actual locations (at the traffic analysis zone (TAZ) level) that generated/attracted these trips. GIS-based transit trip allocation methods are developed with a focus on considering the case when the access shed spans multiple TAZs. The proposed methods improve practical applicability with easily obtained data. The performance of the proposed allocation methods is further evaluated using transit on-board survey data. The results show that the methods can effectively handle various conditions, particularly for major activity generators. The average errors between observed data and the proposed method are about 8% for alighting trips and 18% for boarding trips.     

大鼠前牙扭转移动后保持期动物模型的建立

目的 建立大鼠实验性正畸前牙扭转移动后保持期的动物模型并分析保持时间与复发距离的关系.方法 采用36只雌性SD大鼠,在上颌两个中切牙间施加20 g的力量,建立牙根扭转的动物模型.10d后进行固定保持,分为1、4、7、14、21d保持组(实验组),并设不予保持的对照组.测量加力结束后、保持结束时和拆除保持器后7d两中切牙...     

采用COM组件计算铁路货物运价里程的设计方案

介绍用COM组件计算铁路货物运价里程的设计方案,分析货物运价里程对象的数据结构,最短路径算法及其在运价里程计算中的具体实现,COM组件的主要技术参数和运行条件.     

交通行为建模－问题与机会

研究交通行为是科学规划与管理交通系统的基础.数学模型是整体把握交通行为的重 要工具.目前的交通行为模型注重适用性.而欠缺理论上的严密性,回顾了交通模型中的几个 经典成就,指出交通科学中还有许多问题等待解决,介绍了国际上传播交通模型的主要媒体.