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Fully autonomous vehicles (AVs) have the potential to considerably change urban mobility in the future. This study simulates potential AV operating scenarios in the Greater Toronto Area (GTA), Canada, and assesses transportation system performance on a regional level. For each scenario, the base capacities of certain types of road links are modified to simulate the theoretical increase in throughput enabled by AV driving behavior. Another scenario examines driverless parking operations in downtown Toronto. Simulation results indicate that the increased attractiveness of freeways relative to other routes leads to slightly increased average travel distance as vehicles divert to access higher capacity road links. Average travel time is found to decrease by up to one-fifth at the 90% AV market penetration level. Concurrently, localized increases in congestion suggest that proactive transportation planning will be needed to mitigate negative consequences of AV adoption, especially in relation to induced demand for personal automobile travel. 相似文献
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Several significant events between 2007 and 2009 impacted flight demands and the abilities of the three major New York area airports to handle demand. This paper assesses the results of applying a probabilistic simulation method – which isolates the individual contributions of changes in flight demand and changes in airport throughput performance to changes in flight delays – to diagnose how these different events may have caused operational changes at these airports, and in turn, how the results may be used to inform policies for appropriate countermeasures. The analysis revealed two key observations. Firstly, certain patterns in throughput performance shifts caused the most significant delays, and were more likely to have been caused by controller staffing issues rather than caps. Secondly, relatively constant average delays from one year to the next may result from significant demand drops accompanied by large throughput performance degradations at an airport. This suggests that not only operational limitations on capacity encourage airlines to reduce schedules, but that changed demands can also impact throughput performance. Overall, the analysis indicates that caps may not have provided their fully intended delay benefits. Although they successfully reduced overall flight demands at LGA and JFK, they also directly limited throughput performance at critical times, in turn limiting delay benefits. In addition, demands at the busiest times of the day appear to be relatively inelastic to these operational limitations, insofar as demand profiles at EWR and JFK remained “peaky” in 2008 and 2009. Also, the recession was largely responsible for reducing demands at the airports in 2009, but the delay benefits of this were dampened by a corresponding throughput performance degradation. Based on the above observations, a more direct demand management policy combined with policies that focus on maintaining high staffing capabilities at critical times of the day may be considered, to reduce the likelihood of major queue formation on days that do experience sustained demands. The results also suggest that a more flexible caps system, particularly during times of heavy queues, could be explored. Although airport practitioners have keen understandings of how their airports operate, without the support of quantitative analysis tools, it can be more difficult to argue the need for appropriate countermeasures. An analysis such as the one presented here can provide the detailed quantitative substantiation required to build cases for these targeted policy directives and infrastructure investments. 相似文献
656.
This article investigates two performance attributes of road networks, reliability and vulnerability, analyzing their similarities as well as the differences that justify distinct definitions, based on consolidation of recent studies. We also discuss the indicators found in the literature for these two performance attributes. Since various authors treat vulnerability as an aspect of reliability instead of a specific attribute, we carried out an application to a complex road network representative of the city of Rio de Janeiro to check the suitability of this approach. The results show that the vulnerability indicators are more strongly affected by the characteristics of alternative routes while the reliability metrics are more sensitive to the congestion level. The conclusion is that reliability and vulnerability should be treated distinctly for evaluating the performance of road network links. 相似文献
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根据提速货车和既有装转8A型转向架的非提速货车低速通过小半径曲线以及12#道岔侧线时的动力学性能测试数据,分析货车低速通过小半径曲线、道岔侧线的动力学性能.结果表明:在正常技术状态下,装用转K2、转K4、转K5、转K6型转向架的提速货车和既有装用转8A型转向架的非提速货车在低速通过小半径曲线和道岔侧线时,货车的动力学性能基本满足要求,货车低速通过小半径曲线有安全保障;对于提速货车,在通过小半径曲线并在出曲线时,由于外轨超高降低、外侧轮减载,从而增加了对车辆安全的不利影响,因此,应严格控制提速货车运行速度在线路规定的允许速度范围内.分析货车通过小半径曲线时每个车轮的轮轨力变化特征可知,提速货车在重车时比空车时的轮轨力增减缓和,更有利于货车通过曲线的安全性;非提速货车在进出曲线时,由于车体的重量通过心盘近似平均地分配到左右侧架上,使得其轮轨力的增减较小且垂向力无明显增减. 相似文献
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刘曙蓉 《电力机车与城轨车辆》2004,27(1):37-39
介绍了统计过程控制(SPC)技术原理,并探讨应用SPC技术对机车配件质量稳定性和过程能力进行分析,达到降低机车配件入厂检验的风险和对供货商进行有效评价和控制的目的。 相似文献
659.
研究目的:湿陷性为黄土的主要工程地质问题,其产生机理极其复杂,产生原因多种多样,需进一步深入研究。研究方法:基于现有文献对黄土的湿陷原因与机理的认识,以甘肃黄土地区高等级公路黄土分区项目为例,利用多元统计分析方法中的因子分析对甘肃陇西陇东地区黄土的59组样本的9个常规试验的物理力学指标数据进行了分析,在此基础上,对黄土湿陷机理内因进行了分析。研究结论:黄土的湿陷性指标与其它物理力学指标存在相关性,同时,揭示出产生湿陷的黄土必须有湿陷空间及一定量遇水强度降低的联接,黄土的疏松性、多孔性正是其反映,特别是支架孔隙是导致黄土湿陷的最主要原因,而非饱和黄土是产生湿陷的前提,粘粒含量及粘土的水-胶联结在产生湿陷过程中的作用需要进一步商榷。此外,本方法解决了常规单因子分析因指标交叉而分析失真的缺陷。 相似文献
660.
本文介绍了船舶主机上引入一种新颖电子控制喷油系统,大大改善了燃烧效率和耗油量问题,并保证了船舶主机的最佳工作性能。文章重点论述了该系统的特点与功能,结构原理及实验测试数据等。 相似文献