临时关闭道路以疏导城市道路交通流的可行性分析

文章基于Braess悖论,以单位车辆的平均出行时间为最优目标,以网络道路系统为约束条件,从逆向思维角度建立了通过临时关闭道路引导交通流以缓解城市道路交通拥挤的Narsh均衡非线性规划模型,并以北京二环道路网络为研究对象进行了实例分析。结果表明,在城市道路网中,关闭部分路段并不能明显缓解交通拥堵现状,但可以在不影响路网整体通行时间的条件下改善路网局部拥堵状况。建议城市道路交通临时疏导方案应该根据路网交通流的分布特点和道路通过能力等因素进行制订。     

基于一、二维水动力耦合模拟的三峡库区溢油预测模型研究

随着三峡库区通航条件的改善和船舶流量的不断增加,库区水上溢油风险形势日益严峻.文中以一维圣维南方程和二维EFDC模型为基础,实现了一维、二维水动力的耦合模拟,而后结合油粒子漂移扩散模型设计了一个适用于三峡库区水上溢油预测模型.在此基础上对175m水位的万州段长江干流的假想溢油事故进行了进行模拟,初步检验了溢油预测模型的效果.     

长江重庆辖区溢油三维虚拟仿真及在应急决策中的应用

长江重庆辖区呈连续弯曲的河道形态,水文航道情况复杂,辖区内水运繁忙,危险化学品运量逐年上升,溢油事故风险不断攀升,建立溢油三维虚拟仿真并应用于决策已成为当务之急.文中通过建立基于油粒子模式的重庆辖区溢油模型,说明溢油三维虚拟仿真过程并建立长江重庆辖区溢油三维虚拟仿真系统,并将该系统应用于应急决策.     

The efficiency of congestion charging: Some lessons from cost–benefit analyses

This paper addresses methodological issues in cost–benefit analysis (CBA) regarding congestion charging schemes. Despite suspicion on the reality of travel time savings, it is argued that these savings are a conservative value of surplus gained from a congestion scheme. The methodology of measurement of travel time reliability is not yet stabilised, but the literature review suggests that it may take a growing share of benefits in the future. Sensitivity tests performed on the London and Stockholm case studies with a simulation model underline the need to accurately measure speeds, while the value of travel time appears less critical. Finally, the impact of costs of public funds on public accounts is greatly significant and may increase in the future.     

基于路网整体多种服务质量的拥挤定价

依据现实路网整体结构中存在多种服务质量等级,一方面要满足不同类型的交通需求,另一方面要使路网交通高效率运行,以达到资源共享的最大化,建立了路径边际成本定价模型。     

Morning commute problem considering route choice, user heterogeneity and alternative system optima

This paper extends the bottleneck model to study congestion behavior of morning commute and its implications to transportation economics. The proposed model considers simultaneous route and departure time choices of heterogenous users who are distinguished by their valuation of travel time and punctual arrival. Moreover, two dynamic system optima are considered: one minimizes system cost in the unit of monetary value (i.e., the conventional system optimum, or SO) and the other minimizes system cost in the unit of travel time (i.e., the time-based SO, or TSO). Analytical solutions of no-toll equilibrium, SO and TSO are provided and the welfare effects of the corresponding dynamic congestion pricing options are examined, with and without route choice. The analyses suggest that TSO provides a Pareto-improving solution to the social inequity issue associated with SO. Although a TSO toll is generally discriminatory, anonymous TSO tolls do exist under certain circumstances. Unlike in the case with homogenous users, an SO toll generally alters users’ route choices by tolling the poorer users off the more desirable road, which worsens social inequity. Numerical examples are presented to verify analytical results.     

Traffic congestion pricing methodologies and technologies

This paper reviews the methods and technologies for congestion pricing of roads. Congestion tolls can be implemented at scales ranging from individual lanes on single links to national road networks. Tolls can be differentiated by time of day, road type and vehicle characteristics, and even set in real time according to current traffic conditions. Conventional toll booths have largely given way to electronic toll collection technologies. The main technology categories are roadside-only systems employing digital photography, tag & beacon systems that use short-range microwave technology, and in-vehicle-only systems based on either satellite or cellular network communications. The best technology choice depends on the application. The rate at which congestion pricing is implemented, and its ultimate scope, will depend on what technology is used and on what other functions and services it can perform.     

拥挤收费下的路网交通评估模型研究

对城市实施拥堵收费策略的评估包括两个方面:一个是公共政策、经济环境、收费方式的技术可行性的评估;二是对拥堵收费区域内外的交通影响进行预估。文章在后一方面展开研究,利用交通网络分析的理论建立了拥挤收费下的交通网络评估模型,提出评估指标和求解算法。数值算例结果验证了评估模型以及算法的合理性,揭示了拥挤收费下收费区域内外交通模式变化的内在联系。表明只有将拥堵收费政策与城市良好的公交服务系统具体结合才能更好地起到减轻拥堵的预期效果。     

溢油污染生物资源损害评估地理信息系统的开发

提出利用VC 从底层开发溢油污染生物资源损害评估地理信息系统,用于实现对模型数据的有效管理和图形可视化.根据数值评估模型应用特点,建立评估模型数据库和地理信息数据库,给出了空间数据和属性数据的管理和查询实现方法.通过应用矢量和栅格空间数据模型、面向对象编程方法以及地图投影变换、图形绘制等图形显示技术实现空间数据的可视化.利用VC 对系统进行开发,除实现了一般GIS的基本功能外,还实现了潮流预报、溢油行为动态预测以及溢油事故海洋生物资源损害评估等专业应用功能.