The identification and empirical characterization of vehicular (Lagrangian) fundamental diagrams in multilane traffic flow

Traditional macroscopic traffic flow modeling framework adopts the spatial–temporal coordinate system to analyze traffic flow dynamics. With such modeling and analysis paradigm, complications arise for traffic flow data collected from mobile sensors such as probe vehicles equipped with mobile phones, Bluetooth, and Global Positioning System devices. The vehicle‐based measurement technologies call for new modeling thoughts that address the unique features of moving measurements and explore their full potential. In this paper, we look into the concept of vehicular fundamental diagram (VFD) and discuss its engineering implications. VFD corresponds to a conventional fundamental diagram (FD) in the kinematic wave (KW) theory that adopts space–time coordinates. Similar to the regular FD in the KW theory, VFD encapsulates all traffic flow dynamics. In this paper, to demonstrate the full potential of VFD in interpreting multilane traffic flow dynamics, we generalize the classical Edie's formula and propose a direct approach of reconstructing VFD from traffic measurements in the vehicular coordinates. A smoothing algorithm is proposed to effectively reduce the nonphysical fluctuation of traffic states calculated from multilane vehicle trajectories. As an example, we apply the proposed methodology to explore the next‐generation simulation datasets and identify the existence and forms of shock waves in different coordinate systems. Our findings provide empirical justifications and further insight for the Lagrangian traffic flow theory and models when applied in practice. Copyright © 2015 John Wiley & Sons, Ltd.     

Building legitimacy for risky policies: The cost of avoiding conflict in Stockholm

The controversial nature of urban congestion charging policies makes them politically risky. Urban planners, policy makers and politicians are forced to consider how they can legitimately introduce a policy that the public may not want. Implementation in London, and failure in Edinburgh, raise questions about whether they should seek full citizen support, or work strategically towards implementation in the face of public opposition.This paper reports on an investigation of the Stockholm congestion charging trial (SCCT). It analyses the strategy developed by the city authorities to create legitimacy for the implementation of the SCCT. The SCCT is examined in two steps, firstly how the ‘trial + referendum’ approach was successful in securing public acceptance, and secondly how key aspects of the design of the trial and the subsequent referendum were adjusted in response to emerging risks, demonstrating the pragmatic approach of the city leaders managing the policy process. The study suggests that the city leaders chose a clearly pragmatic approach, grounded in compromise, yet subtly designed to avoid openly confronting the status quo. The strategy was continuously adapted and adjusted, in the face of emerging risks, and clearly served to create consensus while avoiding difficult questions of urban mobility.     

Benefit of speed reduction for ships in different weather conditions

Currently, the shipping industry is facing a great challenge of reducing emissions. Reducing ship speeds will reduce the emissions in the immediate future with no additional infrastructure. However, a detailed investigation is required to verify the claim that a 10% speed reduction would lead to 19% fuel savings (Faber et al., 2012).This paper investigates fuel savings due to speed reduction using detailed modeling of ship performance. Three container ships, two bulk carriers, and one tanker, representative of the shipping fleet, have been designed. Voyages have been simulated by modeling calm water resistance, wave resistance, propulsion efficiency, and engine limits. Six ships have been simulated in various weather conditions at different speeds. Potential fuel savings have been estimated for a range of speed reductions in realistic weather.It is concluded that the common assumption of cubic speed-power relation can cause a significant error in the estimation of bunker consumption. Simulations in different seasons have revealed that fuel savings due to speed reduction are highly weather dependent. Therefore, a simple way to include the effect of weather in shipping transport models has been proposed.Speed reduction can lead to an increase in the number of ships to fulfill the transport demand. Therefore, the emission reduction potential of speed reduction strategy, after accounting for the additional ships, has been studied. Surprisingly, when the speed is reduced by 30%, fuel savings vary from 2% to 45% depending on ship type, size and weather conditions. Fuel savings further reduce when the auxiliary engines are considered.     

Increasing the accuracy of trip rate information from passive multi-day GPS travel datasets: Automatic trip end identification issues

With the availability of Global Positioning System (GPS) receivers to capture vehicle location, it is now feasible to easily collect multiple days of travel data automatically. However, GPS-collected data are not ready for direct use in trip rate or route choice research until trip ends are identified within large GPS data streams. One common parameter used to divide trips is dwell time, the time a vehicle is stationary. Identifying trips is particularly challenging when there is trip chaining with brief stops, such as picking up and dropping off passengers. It is hard to distinguish these stops from those caused by traffic controls or congestion. Although the dwell time method is effective in many cases, it is not foolproof and recent research indicates use of additional logic improves trip dividing. While some studies incorporating more than dwell time to identify trip ends having been conducted, research including actual trip ends to evaluate the success of trip dividing methods used have been limited. In this research, 12 ten-day real-world GPS travel datasets were used to develop, calibrate and compare three methods to identify trip start points in the data stream. The true start and end points of each trip were identified in advance in the GPS data stream using a supplemental trip log completed by the participants so that the accuracy of each automated trip division method could be measured and compared. A heuristic model, which combines heading change, dwell time and distance between the GPS points and the road network, performs best, correctly identifying 94% of trip ends.     

高压水自动清洗作业井架(车)工艺装备研究与设计

介绍了一种以高压水射流技术为核心技术的自动清洗工艺装备，用于实现对油田作业井架（车）等大型设备进行自动化清洗。     

The impact of weather conditions on bikeshare trips in Washington,DC

Bicycle usage can be affected by colder weather, precipitation, and excessive heat. The research presented here analyzes the effect of weather on the use of the Washington, DC, bikeshare system, exploiting a dataset of all trips made on the system. Hourly weather data, including temperature, rainfall, snow, wind, fog, and humidity levels are linked to hourly usage data. Statistical models linking both number of users and duration of use are estimated. Further, we evaluate trips from bikeshare stations within one quarter mile of Metro (subway) stations at times when Metro is operating. This allows us to determine whether Metro serves as a back-up option when weather conditions are unfavorable for bicycling. Results show that cold temperatures, rain, and high humidity levels reduce both the likelihood of using bikeshare and the duration of trips. Trips taken from bikeshare stations proximate to Metro stations are affected more by rain than trips not proximate to Metro stations and less likely when it is dark. This information is useful for understanding bicycling behavior and also for those planning bikeshare systems in other cities.     

Behavioural implications of preferences, risk attitudes and beliefs in modelling risky travel choice with travel time variability

The appropriate interpretation of a behavioural outcome requires allowing for risk attitude and belief of an individual, in addition to identification of preferences. This paper develops an Attribute-Specific Extended Rank-Dependent Utility Theory model to better understand choice behaviour in the presence of travel time variability, in which these three important components of choice are empirically addressed. This framework is more behaviourally appealing for travel time and travel time variability research than the traditional approach in which risk attitude and belief are overlooked. This model also reveals significant unobserved between-individual heterogeneity in preferences, risk attitudes and beliefs.     

The planning of aircraft routes and flight frequencies in an airline network operations

This research is aimed at developing a model that maximizes system profit when determining the aircraft routes and flight frequencies in a network. The model employs network flow techniques to effectively collect or deliver passenger flows from all origins to all destinations using non‐stop and multi‐stop flights in multi‐fleet operations. The model was formulated as a multi‐commodity network flow problem. A Lagrangian‐based algorithm was developed to solve the problem. To test the model in practice, a case study is presented.     

GPS-based optimization of plug-in hybrid electric vehicles’ power demands in a cold weather city

Using the WPG03 duty cycle developed from global positioning data collected in Winnipeg, Canada, real world energy demands and costs are modeled. Three types of plug-in hybrid electric vehicles, four temperatures and two charging scenarios are compared to a vehicle with an internal combustion engine. Cold temperatures are shown to greatly affect vehicle operation energy costs, which is an important consideration for cold weather cities such as Winnipeg. The largest energy cost savings are obtained for smaller-battery plug-in hybrids that had the opportunity to charge during the day.     

无线测风仪在索道线路中的应用

风是影响索道安全运行的一大因素。本文介绍了一种结构简单而适用的无线测风仪在索道线路上应用的效果。     

Influence of the weather on mode choice in corridors with time-varying congestion: a mixed data study

Studies that link human behaviour to the influence of weather have historically been conducted in such fields as tourism, marketing and leisure. In most studies that jointly examine weather and the mode of transport, only open-air transportation has been considered (for example, bicycle, motorcycle or walking). This focus, together with the habitual use of data collected with automatic devices and a lack of studies that analyse this issue using stated preference data, are the main reasons motivating this paper. This paper aims to analyse the influence of weather and the density of traffic on the choice of transport mode. A case study is conducted in an access/egress corridor located in the city of Barcelona (Spain). Two data sources were used: revealed preference and stated preference data. Modelling techniques using mixed data enabled the stronger features from both data sources to be captured. Finally, we discuss how the selection of different alternative specific constants in models estimated using mixed data could generate unrealistic forecasting results if environmental changes are expected in the actual market.     

GMAW自动焊在工厂管道预制生产中的应用

文中介绍了GMAW自动焊在工厂管道预制中的应用,比较了与其他焊接方法的优缺点。阐述了GMAW自动焊所需要的设备、工艺要求。详细介绍了保护气体、熔滴过渡形式、焊接住置对焊接的影响。以2种常用材料SAl06Gr．B和304L为例,对坡口准备,所用焊材、电流、电压、保护气做了详细的说明,同时指出在工厂GMAW自动焊接工程中应注意的问题。对采用该种工艺的焊缝进行力学性能试验,各项指标均符合标准要求,完全满足实际生产的需要。     

Automatic fare collection in transit: a synthesis of current practice

Many industries are keeping pace with changing technology in an effort to improve operating efficiency and attract consumers with innovations. The transit industry is no exception, one example being the installation and operation of automatic fare‐collection (AFC) systems. There are many issues to consider in implementing an AFC system, including the type of equipment required and the expected quality of system performance.

This article presents a synthesis of several sources of information pertaining to AFC operations. It includes a discussion of system requirements, and the advantages and disadvantages of system operation. Performance measures of reliability and maintainability are also defined, and AFC systems are evaluated using these measures. Several conclusions are reached concerning current AFC practice.     

支线机场火灾自动报警系统设计与分析

支线机场内的建筑种类繁杂且体量差异较大,给火灾自动报警系统的设计带来一定困扰.本文在梳理相关规范的基础上,结合实际典型工程,通过合理配置消防分控制室,实现了运营管理的便捷与经济成本的节约.为今后此类工程提供了设计思路及参考方案.     

SPS在输油管道压力自动控制系统的应用

为研究输油管道压力自动控制系统中两种调节方式（节流调节、变速调节）的应用效果,结合肯尼亚1号线成品油管道,选用SPS软件,分别对出站控制阀节流调节和离心泵转速调节进行了模拟.得出结论：该管道在设计输量下,采用转速作为调节方式较节流调节更经济.通过对比两种调节方式下泵输出参数,分析出调速节能的原理在于提高了泵机组的能量利用率,使电机输出功率与泵扬程满足工况的要求即可,出站控制阈全开,避免了节流损失.     

Investigating preference heterogeneity in Value of Time (VOT) and Value of Reliability (VOR) estimation for managed lanes

This paper presents an empirical study in investigating user heterogeneity of Value of Time (VOT) and Value of Reliability (VOR). Combined Revealed Preference (RP) and Stated Preference (SP) data were used to understand traveler choice behavior regarding the usage of managed lanes (MLs). The data were obtained from the South Florida Expressway Stated Preference Survey, which focused on automobile drivers who had traveled on the I-75, I-95, or SR 826 corridors in South Florida. Mixed logit modeling was applied and indicated an average value of $13.55 per hour for VOT and $16.13 per hour for VOR. Potential sources of heterogeneity in user sensitivities to time, reliability, and cost were identified and quantified by adding interaction effects of the variables in the mixed logit model. The findings indicated that various socioeconomic demographic characteristics and trip attributes contributed to the variations in VOT and VOR at different magnitudes. The results of this study contribute to a better understanding on what attributes lead to higher or lower VOT and VOR and to what extent. These findings can be incorporated into the demand forecasting process and lead to better estimates and enhanced analytical capabilities in various applications, such as toll feasibility studies, pricing strategy and policy evaluations, and impact analysis.     

班线开发中的资源整合

长途班线除了经营主体多小散、竞争过度、集约化程度低下外,还面临着铁路全面提速的压力.长途班线的开发应具有前瞻性和可行性,老线的整合和长线的改造势在必行."网络整合、共享市场、系统集成"是公路长途客运资源有效配置的内在要求.     

防雷器远程自动无线监控系统在高速公路机电系统中的应用

文章介绍了防雷器远程自动无线监控系统的系统构成及工作模式,阐述了该系统的技术优点、使用局限性及成本控制措施,并结合广西高速公路工程应用实例,提出了该系统在高速公路机电系统建设中的应用方式与前景。     

自控阀室绝缘接头失效检测方法分析

文中结合实际案例,介绍了uDL2电位法、地电位法、绝缘接头测试仪法、PCM漏电率法和电流环法在绝缘接头绝缘性能评价中的应用。结果表明:综合应用5种测试方法,可实现对绝缘接头绝缘性能的定量评价。电流环测试法可直观检测出绝缘接头两侧的管中电流大小及方向,测试结果可靠性最高。