Modeling travel mode choice of young people with differentiated E-hailing ride services in Nanjing China

E-hailing ride service (ERS) has become increasingly popular globally and is changing the urban mobility landscape. There is insufficient research effort in understanding the impact of ERS on travel behavior, in particular among young people. This paper aims to start filling that research gap by first collecting mode choice preference data through a stated preference survey in City of Nanjing, China and then applying nested logit (NL) models and a series of post-estimation analysis to address a number of key research questions of mode choice behavior without and with ERS. Three ERS modes are considered in the Chinese context: DiDi Taxi (D-Taxi), DiDi Express (D-Express), and DiDi Premier (D-Premier), all provided by DiDi Chuxing, the dominant ERS service provider in China. The study finds that age makes little difference in mode choice preference when ERS is introduced between the two age groups considered (18–30 and 31–45). The study results also suggest that young travelers are naturally drawn to ERS for what it represents (a technology innovation) and its business (pricing) model. ERS appears to be a competitive alternative to the conventional modes especially when they are under performed. The study also finds that ERS will likely increase vehicle kilometers traveled (VKT) considerably, which will lead to increase in on-road vehicular emissions, unless some mechanism to switch users to ridesharing is in place.     

全站仪坐标导线的坐标转换法平差及应用

根据线路测量的特点,对全站仪坐标导线计算进行研究。提出了一种利用坐标转换原理直接对全站仪所测得的坐标进行平差计算的方法。通过实例证明,该方法具有计算简单、快速、精度高等优点。同时,根据该原理,给出了测站坐标差限值,从而实现了全站仪坐标导线的现场检核。     

对公路曲线测设中某些常用公式表达形式的商榷

针对目前曲线测设中较常用的计算工具 ,提出了在虚交、缓和曲线、外距计算中运有较方便的公式表达形式     

公路桥涵勘测设计中的常见问题及其对策

在公路桥涵勘测设计理念中,主体思想是将排水系统、行车机制以及通航体系融入到桥涵建设中.针对实施桥涵勘测工作中通常会遇到的桥涵水毁、土质松软等不利因素,提出一套合理化勘测策略和勘测管理机制的改进建议,以优化勘测技术、推动桥涵勘测工作的有序发展.     

GPS实时动态测量技术在山区地震勘探中的应用研究

探讨了应用实时动态ＧＰＳ测量技术（ＲＴＫＧＰＳ）在山地地震勘察中应用的有关问题,并就新疆和四川两地区的数据进行了比较分析,认为采用ＲＴＫ实时动态测量系统进行山区地震勘探测量,质量安全可靠。     

一种单霍尔信号及电流采样的车窗防夹方案

介绍单霍尔信号判断车窗位置原理、电机电流采样的防夹设计原理、双继电器驱动控制单霍尔电机原理和电流采样标定车窗防夹力原理。     

基于碰撞安全性的铝合金吸能盒轻量优化

本文中以一种匹配碳纤维复合材料保险杠防撞梁的吸能盒为研究对象,通过试验设计优化,获得吸能盒最佳锥角和溃缩孔的直径及其排列;然后采用拉丁超立方抽样和基于Kriging代理模型加点策略的多目标粒子群优化算法对吸能盒厚度进行多目标优化.优化后不仅吸能盒吸能量大幅提升,且吸能盒质量明显下降.刚性壁100％重叠率正面碰撞和25％...     

三维道路软件程序在施工测量的应用

公路工程施工测量工作的准确性和效率的高低是公路工程项目施工管理的重要问题。文中就汕揭(汕头至揭阳段)高速公路第八合同段三维道路软件程序在施工测量中边坡放样的应用实例,浅谈如何利用较好的测量软件程序来提高施工测量的准确程度和工作效率。     

Strategic sampling for large choice sets in estimation and application

Many discrete choice contexts in transportation deal with large choice sets, including destination, route, and vehicle choices. Model estimation with large numbers of alternatives remains computationally expensive. In the context of the multinomial logit (MNL) model, limiting the number of alternatives in estimation by simple random sampling (SRS) yields consistent parameter estimates, but estimator efficiency suffers. In the context of more general models, such as the mixed MNL, limiting the number of alternatives via SRS yields biased parameter estimates. In this paper, a new, strategic sampling scheme is introduced, which draws alternatives in proportion to updated choice-probability estimates. Since such probabilities are not known a priori, the first iteration uses SRS among all available alternatives. The sampling scheme is implemented here for a variety of simulated MNL and mixed-MNL data sets, with results suggesting that the new sampling scheme provides substantial efficiency benefits. Thanks to reductions in estimation error, parameter estimates are more accurate, on average. Moreover, in the mixed MNL case, where SRS produces biased estimates (due to violation of the independence of irrelevant alternatives property), the new sampling scheme appears to effectively eliminate such biases. Finally, it appears that only a single iteration of the new strategy (following the initialization step using SRS) is needed to deliver the strategy’s maximum efficiency gains.     

沥青路面车辙钻芯取样试验研究

文章通过对某试验路段车辙凹陷位置及隆起位置进行钻芯取样试验,分析了沥青路面车辙不同位置处芯样的厚度、毛体积密度、油石比、级配的变化规律,为高速公路沥青路面车辙研究提供参考。