中国交通运输业能源回弹效应研究

为厘清中国交通运输业能源消耗量攀升的原因,本文应用中国交通运输业1991-2014年的数据,基于超越对数生产函数估计出各投入要素的产出弹性和技术进步对产出增长的贡献率,进而测算出中国交通运输业的能源回弹效应.研究结果表明,样本期内中国交通运输业存在较为严重的要素错配与效率损失;中国交通运输业仅有少数年份出现了回弹效应,且有"回火"情形出现;多数年份里中国交通运输业由于能源效率无改善或技术无进步而未形成能源回弹效应,中国交通运输业能源消耗量攀升的主要原因在于行业"高增长、高能耗"的粗放式发展方式.     

城市轨道交通两线换乘形式及便捷性研究

通过研究城市轨道交通两线换乘车站站位关系、乘客换乘路径和站台型式组合三大要素,基于综合叠加后形成的换乘形式,对城市轨道交通两线换乘的便捷性进行分析。依据换乘距离计算结果,在不考虑客流分布特征等其他外部因素时,同站台换乘便捷性最高,垂直平行比水平平行便捷性更好;十字型、T型、L型换乘便捷性依次降低,在线路相交时应优先选择十字型;虚T型、虚L型和分离式换乘便捷性较低,主要取决于换乘通道长度。无论采用何种换乘形式,为便于统筹协调资源和提高运作效率,建议换乘车站实行一体化管理,在管理界面、设备设施两个维度做好切分。     

An aircraft boarding model with the group behavior and the quantity of luggage

A reasonable boarding model can effectively improve the boarding efficiency. Therefore, developing boarding models/strategies to improve the boarding efficiency has been an interesting topic in the air transportation. In this paper, we incorporate the group behavior and the quantity of luggage into the boarding process, and then develop an extended boarding model to investigate the effects of the two factors on the delay time and boarding time. The numerical results show that the quantity of luggage may make each passenger’s boarding behavior more complex, while the group behavior can shorten some passengers’ delay time and the total boarding time. The results can help administrators organize the boarding process and enhance the boarding efficiency.     

Eco approaching at an isolated signalized intersection under partially connected and automated vehicles environment

This research proposed an eco-driving system for an isolated signalized intersection under partially Connected and Automated Vehicles (CAV) environment. This system prioritizes mobility before improving fuel efficiency and optimizes the entire traffic flow by optimizing speed profiles of the connected and automated vehicles. The optimal control problem was solved using Pontryagin’s Minimum Principle. Simulation-based before and after evaluation of the proposed design was conducted. Fuel consumption benefits range from 2.02% to 58.01%. The CO₂ emissions benefits range from 1.97% to 33.26%. Throughput benefits are up to 10.80%. The variations are caused by the market penetration rate of connected and automated vehicles and v/c ratio. No adverse effect is observed. Detailed investigation reveals that benefits are significant as long as there is CAV and they grow with CAV’s market penetration rate (MPR) until they level off at about 40% MPR. This indicates that the proposed eco-driving system can be implemented with a low market penetration rate of connected and automated vehicles and could be implemented in a near future. The investigation also reveals that the proposed eco-driving system is able to smooth out the shock wave caused by signal controls and is robust over the impedance from conventional vehicles and randomness of traffic. The proposed system is fast in computation and has great potential for real-time implementation.     

Increased energy efficiency in short sea shipping through decreased time in port

According to a range of assessments, there exists a large cost-effective potential to increase energy efficiency in shipping through reduced speed at sea enabled by shorter time in port. This means that the energy needed can be reduced whilst maintaining the same transport service. However, the fact that a large cost-effective potential has been identified that is not being harnessed by decision-makers in practice suggests that there is more to this potential to understand. In this paper, the possibilities for increasing energy efficiency by reducing waiting time in port are explored and problematised through a case study of a short sea bulk shipping company transporting dry bulk goods mainly in the North and Baltic seas. Operational data from two ships in the company’s fleet for one year showed that the ships spent more than 40% of their time in ports and that half of the time in port was not productive. The two most important reasons for the large share of unproductive time were that ports were closed on nights and weekends and that ships arrived too early before the stevedores were ready to load or unload the cargo. Reducing all of the unproductive time may be difficult, but the results also show that even a conservative estimate of one to four hours of reduced time per port call would lead to a reduction in energy use of 2–8%. From in-depth interviews with employees of the shipping company, ports and ship agencies, a complex picture is painted when attempting to understand how this potential arises. Aspects such as a lack of effective ship-shore-port communication, little time for ship operators, an absence of means for accurately predicting energy use of voyages as a function of speed, perceived risk of arriving too late, and relationships with third-party technical management may all play a role.     

Regional climate impact of aerosols emitted by transportation modes and potential effects of policies on demand and emissions

The transportation system is one of the main sectors with significant climate impact. In the U.S. it is the second main emitter of carbon dioxide. Its impact in terms of emission of carbon dioxide is well recognized. But a number of aerosol species have a non-negligible impact. The radiative forcing due to these species needs to be quantified. A radiative transfer code is used. Remote sensing data is retrieved to characterize different regions. The radiative forcing efficiency for black carbon are 396 ± 200 W/m²/AOD for the ground mode and 531 ± 190 W/m²/AOD for the air transportation, under clear sky conditions. The radiative forcing due to contrail is 0.14 ± 0.06 W/m² per percent coverage. Based on the forcing from the different species emitted by each mode of transportation, policies may be envisioned. These policies may affect demand and emissions of different modes of transportation. Demand and fleet models are used to quantify these interdependencies. Depending on the fuel price of each mode, mode shifts and overall demand reduction occur, and more fuel efficient vehicles are introduced in the fleet at a faster rate. With the introduction of more fuel efficient vehicles, the effect of fuel price on demand is attenuated. An increase in fuel price of 50 cents per gallon, scaled based on the radiative forcing of each mode, results in up to 5% reduction in emissions and 6% reduction in radiative forcing. With technologies, significant reduction in climate impact may be achieved.     

基于认知行为方法改善睡眠及促进职工身心健康的研究──以中国铁路广州局集团有限公司为例

随着公司制改革,国铁正向现代运输经营型企业转型,生产力的快速发展和组织变革既是机遇也是挑战。有效调适身心,适应不断变化的环境,促进职工身心健康,已成为实施健康中国发展战略的需求。本文阐述了铁路企业关注职工身心健康的现实意义,分析了现阶段企业职工身心健康存在的突出问题及成因,记录了实践活动开展过程及收效,提出了相应做法和对策。经多年调查发现,睡眠问题已成为困扰职工身心健康的突出隐患,因此率先在铁路企业中引入失眠的认知行为疗法(CBTI),结合运用多种心理学方法,招募志愿者开展小组实验,以促进职工睡眠质量,提升睡眠效率。希望通过实践活动的推广和长期坚持,从根本上改善职工睡眠质量,提高身心健康水平,为铁路安全生产构筑"心"的屏障。     

Interface design considerations for an in-vehicle eco-driving assistance system

This high-fidelity driving simulator study used a paired comparison design to investigate the effectiveness of 12 potential eco-driving interfaces. Previous work has demonstrated fuel economy improvements through the provision of in-vehicle eco-driving guidance using a visual or haptic interface. This study uses an eco-driving assistance system that advises the driver of the most fuel efficient accelerator pedal angle, in real time. Assistance was provided to drivers through a visual dashboard display, a multimodal visual dashboard and auditory tone combination, or a haptic accelerator pedal. The style of advice delivery was varied within each modality. The effectiveness of the eco-driving guidance was assessed via subjective feedback, and objectively through the pedal angle error between system-requested and participant-selected accelerator pedal angle. Comparisons amongst the six haptic systems suggest that drivers are guided best by a force feedback system, where a driver experiences a step change in force applied against their foot when they accelerate inefficiently. Subjective impressions also identified this system as more effective than a stiffness feedback system involving a more gradual change in pedal feedback. For interfaces with a visual component, drivers produced smaller pedal errors with an in-vehicle visual display containing second order information on the required rate of change of pedal angle, in addition to current fuel economy information. This was supported by subjective feedback. The presence of complementary audio alerts improved eco-driving performance and reduced visual distraction from the roadway. The results of this study can inform the further development of an in-vehicle assistance system that supports ‘green’ driving.     

Reducing the energy consumption of heavy goods vehicles through the application of lightweight trailers: Fleet case studies

Reducing the empty weight of articulated heavy goods vehicle trailers is one avenue that needs to be explored in reducing the carbon footprint of the road freight industry as a whole. A statistical analysis of two heavy goods vehicle fleets operating in the United Kingdom has helped to identify double-deck trailers used in grocery haulage and ‘walking-floor’ trailers used in bulk haulage as two examples of trailers that can benefit significantly from lightweighting. Energy consumption of numerous articulated heavy goods vehicles is quantified through an idealised drive cycle analysis reflecting a long haul journey over a highway. This energy analysis allows for a mass energy performance index to be established. The analysis has shown that reducing the empty weight of trailers by 30% can cause reductions of up to 18% and 11% in mass energy performance index for double-deck trailers and ‘walking-floor’ trailers respectively. Using this approach, trailers that will benefit the most from weight reduction can be identified systematically, allowing for lightweighting strategies to be implemented more effectively. Strategies to reduce empty trailer weight and improve vehicle utilisation are also discussed.     

Impact of road gradient on energy consumption of electric vehicles

We investigate the impact of road gradient on the electricity consumption of electric vehicles (EVs) by combining long-term GPS tracking data with digital elevation map (DEM) data for roads in Aichi prefecture, Japan. Eight regression models are constructed and analysed to compare the differences between linear and logarithmic forms of trip energy consumption, differences between considering the road gradient or not, and differences between considering the fixed effects of EVs or not. By categorizing gradients and assigning a percentage of the trip distance to each category, a significantly better model of electricity consumption can be achieved. The results of this study are a novel contribution toward understanding the challenges and benefits associated with downgrade braking on energy regeneration.