Classifying the purpose of stopped truck events: An application of entropy to GPS data

This paper applies the concept of entropy to mine large volumes of global positioning system (GPS) data in order to determine the purpose of stopped truck events. Typical GPS data does not provide detailed activity information for a given stop or vehicle movement. We categorize stop events into two types: (1) primary stops where goods are transferred and (2) secondary stops where vehicle and driver needs are met, such as rest stations. The proposed entropy technique measures the diversity of truck carriers with trucks that dwell for 15 min or longer at a given location. Larger entropy arises from a greater variety of carriers and an even distribution of stop events among these carriers. An analysis confirms our initial hypothesis that the stop locations used for secondary purposes such as fuel refills and rest breaks tend to have higher entropy, reflecting the diversity of trucks and carriers that use these facilities. Conversely, primary shipping depots and other locations where goods are transferred tend to have lower entropy due to the lower variety of carriers that utilize such locations.     

小松PC系列挖掘机液压伺服系统恒功率控制分析

通过对小松PC系列挖掘机液压伺服系统的工作原理和工作过程分三种情况进行阐述,对小松PC系列挖掘机液压伺服系统恒功率控制进行了分析。     

基于停车视距的高速公路雨天行车安全车速研究

考虑低能见度及路面附着系数减小的情况,研究了高速公路雨天的安全车速.从跟车状态下停车过程出发,根据不同的水膜厚度得出其对应的附着系数,进行了基于AASHTO停车视距模型的高速公路安全车速计算.并应用于湖北省黄黄高速公路雨天交通管理措施,供相关技术人员参考.     

平面十字交叉口停车线设计方法研究

城市道路交叉口停车线设计是影响交叉口通行秩序的重要因素之一。本文通过对平面十字交叉口的观测及分析,总结现状交叉口停车线设计的基本模式及问题,提出基于通行条件约束的交叉口停车线设计的实现目标及约束条件。将交叉口停车线设计理论化,给出平面十字交叉口停车线设计的基本模型。最后分析影响停车线设计的因素,并总结规律。在应用方面选择厦门市一个典型十字交叉口进行设计,以检验停车线设计模型的可行性。     

Optimization of bus stop locations for improving transit accessibility

A mathematical model is developed in this paper to improve the accessibility of a bus service. To formulate the optimization model, a segment of a bus route is given, on which a number of demand entry points are distributed realistically. The objective total cost function (i.e. the sum of supplier and user costs) is minimized by optimizing the number and locations of stops, subject to non‐additive users' value of time. A numerical example is designed to demonstrate the effectiveness of the method thus developed to optimize the bus stop location problem. The sensitivity of the total cost to various parameters (e.g. value of users' time, access speed, and demand density) and the effect of the parameters on the optimal stop locations are analyzed and discussed.     

基于“开放性信息流”公交站牌概念设计探讨

本文系统地分析了国内普通公交站牌普遍存在的信息不全和人性化程度较低等问题。针对公交站牌的主要问题,从信息全面和乘客“受控能力”的基本思想出发,提出了新型公交站牌的基本概念设计思路。通过采用开放式的信息流表达方式,结合区域内公交线网分布图,运用站点索引和线路索引两种查询方式来指引乘客乘坐公交。通过新型公交站牌,乘客不仅可以获得公交线路的信息,还可以获得整个城市的重要公交站点、客运枢纽站和地理位置信息等。设计概念与传统的公交站牌设计思路相比,更加体现了“以人为本”和“以顾客为关注焦点”的理念。     

基于北斗的节能型智能公交电子站牌的开发及应用

解决“市民出行难”问题一直是政府部门关注的民生问题,实现公交信息化是解决“出行难”问题的重要环节和出路.本文提出了一种基于北斗导航系统的节能型智能公交电子站牌系统结构设计方案,有利于市民选择公交作为出行方式.同时,能提升公交公司的服务水平和质量。     

Urban real-world driving traffic emissions during interruption and congestion

On-road emissions from urban traffic during interrupted and congested flow conditions are too high as compared to free-flow condition and often influenced by accelerating and decelerating speed due to frequent stop-and-go. In this study, we measured emissions from passenger cars and auto-rickshaws during peak and off-peak hours and analyzed according to different mileages with the instantaneous speed and acceleration for interrupted and congested traffic conditions. It was found that during flow, several short-events lasting over fractions of a second each lead to a sharp increase in pollutant emissions, indicating episodic conditions. The emission levels are sensitive to frequency and intensity of acceleration and deceleration, in accordance with the traffic-flow patterns and speed, besides mileages. Further, congestion conditions occur during both peak and off-peak hours, but last for different durations. The results are important in the sense that instantaneous estimates of pollutant emissions are necessary for the assessment of air quality in urban centers and for an effective traffic management plan.     

On development of arterial fundamental diagrams based on surrogate density measures from adaptive traffic control systems utilizing stop-line detection

A promising framework for understanding flow-density relationship in traffic flow theory is the Fundamental Diagram, originally developed for uninterrupted traffic flow facilities. The concept has been extended to the Arterial Fundamental Diagram (AFD), which has shown that the same relationship holds on arterial streets. However, constructing an AFD is subject to considerable variability in the measured quantities, due to the highly cyclical nature of signalized intersections. In most cases, these diagrams are based on the data from upstream detectors, located away from traffic signals. Recent scientific literature has shown a value of using stop-line detection data to develop AFDs, opening a plethora of opportunities to further investigate traffic dynamics utilizing the data from adaptive traffic control systems (ATCSs). This can, however, be problematic for two major reasons. First, the data may come from detectors unfit to provide good-quality inputs to develop an AFD. Second, such ATCSs may use their own surrogate measures of density and traffic flow, primarily developed for the purpose of controlling traffic, which may be inappropriate for developing fundamental relationships. This study aims to address these issues by investigating appropriateness of using Degree of Saturation (DS), a density-like measure from Sydney Coordinated Adaptive Traffic System (SCATS), to develop an AFD. Empirical SCATS data shows an interesting pattern of the AFD, which cannot be explained by the data itself. Hence, we derive a new analytical model of DS based on the high-resolution signal and detection data, which reveals parameters that drive its behavior. Additionally, we develop the Cyclical Vehicle Arrival and Discharge Model to simulate SCATS-like operations and derive causal relationships between traffic flow variables and density-like performance measures in a controlled environment. The findings show that DS does not have to be a poor estimator of traffic conditions, but when it is combined with SCATS-measured traffic flows it gives a false representation of near-capacity and over-saturated conditions.     

公交停靠站站台宽度的研究

本文在分析轨道交通站台宽度计算模型对公共交通的不适应性的基础上,提出了公交停靠站宽度计算的基本模型,并通过对站台候车区影响因素的分析,以数学建模的思路对站台候车区的宽度进行了重点研究,最终建立公交停靠站站台宽度的计算模型。研究结果表明站台宽度与候车区乘客的分布状态、每辆公交车的平均上车人数以及各站台泊位的停靠线路数有着明显的关系,计算模型基本与实际相符,具有较强的可操作性。