Does traffic-related calibration of car-following models provide accurate estimations of vehicle emissions?

Fuel consumption or pollutant emissions can be assessed by coupling a microscopic traffic flow model with an instantaneous emission model. Traffic models are usually calibrated using goodness of fit indicators related to the traffic behavior. Thus, this paper investigates how such a calibration influences the accuracy of fuel consumption and NOx and PM estimations. Two traffic models are investigated: Newell and Gipps. It appears that the Gipps model provides the closest simulated trajectories when compared to real ones. Interestingly, a reverse ranking is observed for fuel consumption, NOx and PM emissions. For both models, the emissions of single vehicles are very sensitive to the calibration. This is confirmed by a global sensitivity analysis of the Gipps model that shows that non-optimal parameters significantly increase the variance of the outputs. Fortunately, this is no longer the case when emissions are calculated for a group of many vehicles. Indeed, the mean errors for platoons are close to 10% for the Gipps model and always lower than 4% for the Newell model. Another interesting property is that optimal parameters for each vehicle can be replaced by the mean values with no discrepancy for the Newell model and low discrepancies for the Gipps model when calculating the different emission outputs. Finally, this study presents preliminary results that show that multi-objective calibration methods are certainly the best direction for future works on the Gipps model. Indeed, the accuracy of vehicle emissions can be highly improved with negligible counterparts on the traffic model accuracy.     

Assessment of motor vehicle use characteristics in three Indian cities

Estimates of emissions and energy consumption by vehicular fleet in India are not backed by reliable values of parameters, leading to large uncertainties. We report new methods, including primary surveys and secondary data sources, to estimate in-use fleet size, annual mileage (kilometers per year), and fuel efficiency of cars and motorised two-wheelers (MTW) for Delhi, and except fleet size and annual mileage of cars, for Visakhapatnam and Rajkot. We estimated that the official number of registered cars and MTW in Indian cities is more than two times the actual number of in-use vehicles. The private vehicular fleet in India is the youngest, its fuel efficiency one of the highest, and annual kilometers travelled is the lowest, compared to many high-income countries, such as the USA and those in European Union. Along with high renewal rate of fleet, the data suggest that it is possible for India to have one of the most fuel-efficient vehicle fleets in the world in the future, if fuel-efficiency standards and fiscal policies to contain growing dieselization are implemented in the country at the earliest.     

白龙核电站厂区道路2~#边坡稳定性综合评价

文章根据白龙核电站厂区道路2#边坡的工程实际情况、坡体结构和岩体结构,采用工程地质类比法、赤平投影图解分析法、强度折减法及极限平衡法对边坡稳定性进行了定性与定量分析,揭示了边坡合理的综合开挖坡角,并提出了相应的边坡排水和防护措施。     

高速公路交通安全水平定量化评价方法浅析

文章根据我国的交通安全现状,提出了基于年公里事故数、百万车年公里事故率、年公里死亡数及百万车年公里死亡率四项评价指标的综合安全度指数定量化评价方法,为高速公路安全水平的改善提供科学依据。     

交通建设项目环境影响综合评价模型及应用

文章以秦岭终南山特长隧道项目为例,通过引入模糊层次综合分析法,建立了基于改进的层次分析法(IAHP),确定权重的交通建设项目环境影响的综合评价模型,论述了该模型的应用过程及其有效性。     

绿色航运发展趋势及燃料电池船舶的应用前景

船舶与港口排放带来了日益严重的环境污染问题,燃料电池作为船舶新能源技术之一,因其效率高、排放清洁、噪声和震动小等优异特性,在船舶节能减排和绿色航运发展中倍受关注。本文分析了我国绿色航运发展趋势,进而介绍了船舶新能源技术和燃料电池技术及特性。综述了燃料电池船舶在国内外的研究与应用进展,重点讨论了燃料电池船舶应用前景,展望了燃料电池船舶的未来发展方向。     

铁路客站规模适应性研究

截至2020年,铁路建设了大量畅通融合、绿色温馨、经济艺术、智能便捷的新客站。这些客站在促进现代化综合交通客运枢纽构建和贯彻站城融合发展理念方面起到了积极的推动作用。同时在运营中也发现了部分客站客流超饱和、部分客站客流欠饱和等发展不平衡不充分的新问题。结合工作实践,采用分区取样调查和对比的方法,通过梳理65座客站客流量情况,从客站功能、区域经济、人文活动等多方面展开分析,提出精确测算、综合考量铁路客站规模的基本方法,对于深化铁路供给侧结构性改革、节省国家铁路建设资金、指导铁路客站设计和建设工作具有的重要作用,对今后铁路客站建设具有较强的参考借鉴意义。     

基于整车能量流分析的 WLTC 循环油耗优化

文章基于一辆搭载增压发动机的整车进行轻型汽车测试循环的能量流试验,确定整车 能量利用与损耗的分布,分析损耗原因及潜在优化方向。应用 GT-Suite 软件平台搭建整车系统仿真模型,用能量流测试数据对模型进行校核,优化能耗,降低世界新型车测试循环油耗。依据仿真优化方案对实车整改,验证节油效果。结果表明,通过优化标定策略、改善冷却水 路与油路循环和优化起燃过程能够降低未燃化学能损失、换热损失和排气能量损失,使轻型汽车测试循环油耗降低了 3.68%。此外,还使发动机冷却水温达到平衡温度的时间缩短了 73 s, 且变速器油温显著升高。     

排气背压对整车燃油经济性影响的试验

排气系统作为发动机附件的重要组成部分,排气背压的大小直接影响到柴油发动机的泵气损失和热效率,从而影响整车燃油经济性的表现。论文通过柴油机台架试验,在额定工况下测得发动机功率和燃油消耗率随排气背压的变化曲线,利用 CRUISE 软件进行整车经济性仿真,通过排气背压对整车燃油经济性的影响,给出排气系统优化方向。     

基于重置成本法下成新率在二手车评估中的应用研究

近几年国内二手车的交易量已突破千万辆。在二手车消费的过程中,就需要对二手车的价值进行科学有效的评估。文章结合国内二手车市场情况,在基于重置成本法中对成新率的影响因素进行权重而得到综合成新率。同时也将影响成新率的其它因素纳入调整系数中进行全面评估,从而对二手车进行全面的评估。