Optimal allocation of turns to lanes at an isolated signal-controlled junction

Conventional design methods require the lane marking patterns, which are painted on ground showing road users the permissible turning directions on different approach lanes, as exogenous inputs to define the traffic stream grouping for analysis. This predefined grouping of traffic movements may restrict the design of signal timings in the optimisation procedures. More recently, a lane-based design method has been developed to relax the lane markings as binary-type control variables in a mathematical programming approach. The lane marking patterns and the signal timings can then be optimised simultaneously in a unified framework. This paper presents an extension work to further relax the numbers of approach lane in traffic arms as new integer variables which can then be optimised to give optimal lane arrangement in various arms of a junction to manage the given traffic demands more efficiently. All well-defined signal timings variables in the phase-based approach as well as the lane marking and lane flow variables in the lane-based approach together with their governing constraints are all preserved in the new formulation for the reserve capacity optimisation of isolated signal-controlled junctions.     

隧道贯通段塌方处理施工技术

文章通过公山隧道贯通段塌方处理技术的实例,从大断面隧道贯通段塌方的原因分析,介绍了隧道塌方的处理方案、施工工序等施工技术。由于本次隧道贯通段塌方的处理采取厂有效方案,保证了施工安全,处理过程中没有出现二次塌方和掉块现象,围岩和结构处于稳定状态,达到了预期的"安全、稳妥、保质、经济"的目的。其成果可供类似隧道的塌方处理参考、借鉴。     

Optimal slack time for timed transfers at a transit terminal

At transit terminals where two routes interchange passengers, total system costs may be reduced by allowing some “slack” time in the vehicle schedules to decrease the probability of missed connections. Transfer cost functions are formulated and used to determine optimal slack time for simple systems with transfers between one bus route and one rail line. Some analytic results are derived for empirical discrete and Gumbel distributions of bus arrival times. Relations between the optimal slack times and headways, transfer volumes, passenger time values, bus operating costs, and standard deviations of bus and train arrivals are also developed numerically using normally distributed arrivals. However, the proposed numerical approach can optimize slack times for any observed arrival distributions. The results provide some guidelines on desirable slack times and show that schedule coordination between the two routes is not worth attempting when standard deviations of arrivals exceed certain levels. Possible extensions of this work are suggested in the last section.     

Use of duration models for predicting vehicular delay at a US/Canadian border crossing

Delays caused by congestion at the US/Canadian border crossing between Washington state and British Columbia have underscored the need for some sort of intervention. One obvious congestion-mitigation measure would be to estimate delay times and then relay this information to motorists so that they could select among alternative border crossing sites, or delay their trips. This paper applies duration models to estimate vehicular delay and demonstrates the usefulness of such models as a basis for a fully automated motorist information system. The paper also explores the flexibility of duration models, in providing estimates of vehicle delay, by using alternate parametric forms and assessing prediction accuracy.     

广州地铁小北站暗挖隧道FBG监测技术研究

文章采用光纤布拉格光栅(FBG)传感技术对广州地铁五号线小北站暗挖区间隧道进行了监测研究,内容包括监测设备比选、监测系统设计、传感器封装及保护、数据处理与分析,最后根据监测数据对隧道在开挖期间初期支护体的内力、温度及与围岩间相互作用关系进行了分析。研究表明,FBG传感技术用于地下工程的监测十分可行,优势明显,应用前景十分广阔。     

大断面黄土隧道土石分界段施工技术

土石分界地层大断面黄土隧道,由于其岩体石质较差,缺乏自稳能力,施工极其困难,安全风险极大.文章结合中南铁路土石分界地层中大断面黄土隧道的施工实践,阐述了大断面黄土隧道土石分界段爆破法施工的技术要点,研究分析了合理的施工开挖顺序、台阶高度和长度,以及围岩量测和施工注意事项.     

石油天然气输送钢管是高新技术产品及其发展方向

原国家经贸委确定石油天然气输送钢管是国家高新技术产品。从输油气工程、板带的冶炼及轧制水平、管线管的制管技术等方面加以阐述,各个焊管企业应做出努力,不辜负高新技术产品的荣誉。     

Why Cost Benefit Analysis is perceived as a problematic tool for assessment of transport plans: A process perspective

Academic discussions on Cost Benefit Analysis (CBA) as an appraisal instrument for integrated land use and transportation plans tend to focus on its technical aspects. However, many issues of CBA also arise from process related matters, especially when assessing integrated plans. Using an inductive research design, we explored how these process related issues play out in Dutch planning practices. In two applied research techniques, focus group sessions and open in depth interviews, we focused on process related issues as perceived by CBA participants ranging from plan makers to CBA testers. This article presents the different perceptions of issues in CBA processes. Through these collected perspectives, we found that these issues are multi-layered and present a number of fundamental dilemmas. After relating our empirical data to theory, we conclude that the biggest challenge lies in decreasing the level of mistrust and communication deficits revealed between plan owners and CBA calculators and their respective frames of thinking when assessing complex integrated land use and transportation plans.