Social welfare analysis of investment public–private partnership approaches for transportation projects

This paper has two objectives: (i) to introduce a new approach in order to gain widespread support for road pricing; and (ii) to develop a detailed social welfare analysis for road pricing schemes. We first describe our novel approach that stimulates public support for road pricing, which we refer to as an investment public–private partnership, or IP3. This approach returns a significant portion of the economic value created by road pricing back to the citizens who own the newly priced facility. We then present a social welfare framework that estimates the benefits and costs of using the IP3 approach on an urban transportation network. A P3 project’s impact on overall social welfare provides a more comprehensive evaluation criterion than the often-used Value for Money (VfM) analysis. Apart from several theoretical studies, a detailed social welfare analysis that includes all major P3 project stakeholders is absent from the literature. We use Fresno, California as our case study in order to conduct a welfare analysis on IP3s. Our results show that system-optimal tolling favors average users, but that government—and consequently taxpayers—should pay for costly tolling systems (negative profits). In contrast, unlimited profit-maximizing tolls raise substantial profits for government, for the infrastructure’s citizen-owners, and for the private sector, but the average user is worse off. From a social-welfare perspective, one should search for a Pareto improvement under which all major stakeholders are better off. Our estimates indicate that a mixed public and private tolling scheme offers such an improvement.     

美国公路的施工管理及养护维修技术

介绍了美国沥青路面的施工管理与控制措施,以及沥青路面的养护和维修技术,对我国的公路建设与管理提出建议。     

广州古代海外贸易历史研究40年回顾(1979-2019)

广州自秦汉以来就是中国连接海外世界的重要枢纽,海外贸易的历史两千多年没有中断。早在20世纪初,便有学者开始关注并研究古代广州海外贸易历史。改革开放40年来,考古材料、传世文物愈加丰富,中外学术交流和跨学科合作日益频繁,文献共享率不断提高,政府加大扶持力度,均推动了该领域研究的深度和广度。本文回顾、总结了近40年广州古代海外贸易历史研究的发展脉络、特点、关注点、主要成果及趋势。     

沙漠地区道路涵洞周围流场规律及积沙特征研究

涵洞作为沙漠地区道路工程路基的重要组成部分之一,是保障道路安全的重要基础设施。但沙漠地区道路涵洞较易发生风沙灾害,故对其进行系统全面研究非常必要。通过对不同来流风速大小和不同来流方向下涵洞进行三维数值模拟,对比分析不同风速、不同来流方向下的涵洞周围积沙特征,并总结相关结论。研究结果和结论:对比不同来流方向下的涵洞流场特征,得出来流与涵洞夹角为20°时涵洞对洞前洞后流场影响最大,洞前有大面积增速区,洞后速度下降最为迅速。对比不同来流大小及方向下的涵洞周围积沙特征,可知随来流风速增大涵洞前积沙先增大后减少;洞腔内部随风速增大积沙会有所增多;洞后积沙随风速增大会明显增加。同一风速下夹角增大洞前积沙明显增多,且夹角越大洞前积沙横移越明显;洞后积沙随夹角增大会明显减小。     

Scheduling lane conversions for bus use on city-wide scales and in time-varying congested traffic

The paper explores what can occur when select street lanes throughout a city are periodically reserved for buses. Simulations of an idealized city were performed to that end. The city’s time-varying travel demand was studied parametrically. In all cases, queues formed throughout the city during a rush, and dissipated during the off-peak period that followed. Bus lanes were activated all at once across the city, and were eventually deactivated in like fashion. Activation and deactivation schedules varied parametrically as well. Schedules that roughly balanced the trip-time savings to bus riders against the added delays to car travelers were thus identified.Findings reveal why activating conversions near the start of a rush can degrade travel, both by car and by bus. Balance was struck by instead activating lane conversions nearer the end of the rush, when vehicle accumulation in the city was at or near its maximum. Most of the time savings to bus riders accrued after the conversions had been left in place for only 30 min. Leaving them for longer durations often brought modest additional savings to bus travelers. Yet, the added delays to cars often grew large as a result.These findings held even when buses garnered high ridership shares. This was the case when lane conversions gradually induced new bus trips among residents who formerly did not travel. It was also true when high ridership was a pre-existing feature of the city. Activating conversions a bit earlier in a rush was found to make sense only if commuters shifted from cars to buses in very large numbers. Findings also unveiled how to fine-tune activation and deactivation schedules to suit a city’s congestion level. Guidelines for scheduling conversions in real settings are furnished. So is discussion on how these schedules might be adapted to daily variations in city-wide traffic states. Roles for technology are discussed as well.     

基于BISAR软件的半柔性复合路面层间粘结力分析

为研究半柔性复合路面层间粘结力对路面结构层应力的影响.通过拟定路面交通量以及材料参数,通过BISAR软件进行设计路面典型结构层计算,设计出以半柔性复合材料作为上面层的典型结构层以及沥青路面结构层,并研究层间粘结对半柔性复合路面弯沉、剪应力、行车方向拉应力和荷载方向拉应力的影响.结果表明层间粘结对半柔性复合路面弯沉、剪应力分布具有一定影响,建议在设计时将层间粘结作为重点考虑指标之一.     

广西公路工程勘察项目管理探讨

文章结合对广西公路工程勘察现状的分析,从成本、进度、质量、安全等方面提出了公路工程勘察项目管理的控制措施,为勘察企业应对工程勘察项目要求,提升市场竞争力提供方法依据。     

大吨位压路机在施工中的应用

文章阐述了徐工的大吨位振动压路机产品设备的性能及设计特点,并对该系列产品在施工中的应用情况进行了介绍,为公路工程施工设备的选取提供参考。     

水泥混凝土路面裂缝的成因及防治

本文首先分析了水泥混凝土路面裂缝的成因,然后根据成因提出了相应的防治措施,以供类似工程参考。     

沥青混合料离析评价新方法

对沥青混合料离析评价方法的研究现状进行了回顾，并基于数字图像处理技术，对沥青混合料中集料的分布状态进行了直接研究，借此评价离析程度。研究结果表明：通过比较截面上一定区域内集料面积累计之和的差异，可以定量地评价沥青混合料的离析程度。