Optimal transit routing with partial online information

This paper studies the routing strategy in a transit network with partial online information at stops. By partial online information, we mean that the arrival time of the incoming transit vehicles is available for a subset of the lines serving a stop. To cope with the partial information assumption, a new routing strategy is proposed and closed form formulae for computing expected waiting times and line boarding probabilities are derived. The proposed strategy unifies existing hyperpath-based transit route choice models that assume either no information or full information. Like many existing models, it ensures optimality when all information is available or the headway is exponentially distributed. The problem of determining the attractive set is discussed for each of the three information cases. In particular, a new heuristic algorithm is developed to generate the attractive set in the partial information case, which will always yield a solution no worse than that obtained without any information. The paper also reveals that, when information is available, an optimal hyperpath may contain cycles. Accordingly, the cause of such cycles is analyzed, and a sufficient condition that excludes cycles from optimal hyperpaths is proposed. Finally, numerical experiments are conducted to illustrate the impact of information availability on expected travel times and transit line load distributions. Among other findings, the results suggest that it is more useful to have information on faster lines than on slower lines.     

The two-echelon time-constrained vehicle routing problem in linehaul-delivery systems considering carbon dioxide emissions

Multi-echelon distribution strategy is primarily to alleviate the environmental (e.g., energy consumption and emissions) consequence of logistics operations. Differing from the long-term strategic problems (e.g., the two-echelon vehicle routing problem (2E-VRP), the two-echelon location routing problem (2E-LRP) and the truck and trailer routing problem (TTRP)) that make location decisions in depots or satellites, the paper introduces a short-term tactical problem named the two-echelon time-constrained vehicle routing problem in linehaul-delivery systems (2E-TVRP) considering carbon dioxide (CO₂) emissions. The linehaul level and the delivery level are linked through city distribution centers (CDCs). The 2E-TVRP, which takes CO₂ emissions per ton-kilometer as the objective, has inter-CDC linehaul on the 1st level and delivery from CDCs to satellites on the 2nd level. The Clarke and Wright savings heuristic algorithm (CW) improved by a local search phase is put forward. The case study shows the applicability of the model to real-life problems. The results suggest that the vehicle scheduling provided by the 2E-TVRP is promising to reduce the CO₂ emissions per ton-kilometer of the linehaul-delivery system. Adjusting the central depot location or developing the loaded-semitrailer demand among O-D pairs to eliminate empty-running of tractors will contribute to reduce the CO₂ emission factor.     

An integrated modelling approach for the bicriterion vehicle routing and scheduling problem with environmental considerations

The consideration of pollution in routing decisions gives rise to a new routing framework where measures of the environmental implications are traded off with business performance measures. To address this type of routing decisions, we formulate and solve a bi-objective time, load and path-dependent vehicle routing problem with time windows (BTL-VRPTW). The proposed formulation incorporates a travel time model representing realistically time varying traffic conditions. A key feature of the problem under consideration is the need to address simultaneously routing and path finding decisions. To cope with the computational burden arising from this property of the problem we propose a network reduction approach. Computational tests on the effect of the network reduction approach on determining non-dominated solutions are reported. A generic solution framework is proposed to address the BTL-VRPTW. The proposed framework combines any technique that creates capacity-feasible routes with a routing and scheduling method that aims to convert the identified routes to problem solutions. We show that transforming a set of routes to BTL-VRPTW solutions is equivalent to solving a bi-objective time dependent shortest path problem on a specially structured graph. We propose a backward label setting technique to solve the emerging problem that takes advantage of the special structure of the graph. The proposed generic solution framework is implemented by integrating the routing and scheduling method into an Ant Colony System algorithm. The accuracy of the proposed algorithm was assessed on the basis of its capability to determine minimum travel time and fuel consumption solutions. Although the computational results are encouraging, there is ample room for future research in algorithmic advances on addressing the proposed problem.     

空间分析方法在航线设计和航路监视中的应用

探讨在电子海图中，使用GIS空间分析函数自动判断计划航线的偏航极限范围内是否存在危险点、线、面的方法，为航线设计起决策参考，在航行过程中，起实时航路监视作用。     

The Hybrid Vehicle Routing Problem

In this paper the Hybrid Vehicle Routing Problem (HVRP) is introduced and formalized. This problem is an extension of the classical VRP in which vehicles can work both electrically and with traditional fuel. The vehicle may change propulsion mode at any point of time. The unitary travel cost is much lower for distances covered in the electric mode. An electric battery has a limited capacity and may be recharged at a recharging station (RS). A limited number of RS are available. Once a battery has been completely discharged, the vehicle automatically shifts to traditional fuel propulsion mode. Furthermore, a maximum route duration is imposed according to contracts regulations established with the driver. In this paper, a Mixed Integer Linear Programming formulation is presented and a Large Neighborhood Search based Matheuristic is proposed. The algorithm starts from a feasible solution and consists into destroying, at each iteration, a small number of routes, letting unvaried the other ones, and reconstructing a new feasible solution running the model on only the subset of customers involved in the destroyed routes. This procedure allows to completely explore a large neighborhood within very short computational time. Computational tests that show the performance of the matheuristic are presented. The method has also been tested on a simplified version of the HVRP already presented in the literature, the Green Vehicle Routing Problem (GVRP), and competitive results have been obtained.     

论铁路车流径路的数学问题

归纳铁路车流径路制定过程中和自动化系统中应用车流径路的数学问题。分别讨论容量无限制交通分配方法数学模型和容量限制交通分配方法数学模型。结合铁路运输管理实际给出适合于铁路管理方式的车流径路制定参照模型及其算法。针对各种运输管理类自动化系统中普遍涉及的车流径路求解方法给出详细数学模型与算法。     

铁路应急通信网络组呼的组播路由算法分析

从建立GSM-R铁路应急通信网络的需要出发,在组播路由算法ODMRP的基础上通过改进,提出1种支持GSM-R铁路应急通信网络组呼的组播路由新算法(REGCA)及其算法流程。在该算法中加入了抑制听者发言、限制洪泛区域以及允许自动加入临时组播等控制策略。使用NS2仿真工具建立武广高铁应急通信系统自组网仿真模型,然后根据模型建立相应的仿真场景,对REGCA算法进行仿真分析。仿真结果表明,采用REGCA算法能够大大减轻网络负载、提高分组投递率、降低端到端传输时延和路由开销;采用REGCA算法在各种仿真场景中的分组投递率均达80%以上,端到端传输平均时延均在0.4s以下,能够满足GSM-R铁路应急通信环境下的组呼要求。     

A Novel Optimal Routing for Navigation Systems/Services Based on Global Navigation Satellite System Quality of Service

The positioning quality of global navigation satellite system (GNSS), or GNSS quality of service (QoS), is a major factor impacting real-time navigation performance. Commonly requested routes (i.e., shortest or fastest) may include areas with poor GNSS QoS, which can subsequently degrade navigation performance. To provide alternative routes with high or acceptable GNSS QoS along a route, a novel optimal routing for navigation systems/services based on GNSS QoS by utilizing integrated GNSS (iGNSS) QoS prediction is presented in this article. New routing criteria based on GNSS QoS are maximum availability, maximum accuracy, maximum continuity, and maximum reliability. Two experiments were conducted to compare GNSS QoS-based routes against shortest routes. In one experiment, routes were simulated, and in another, generated routes based on GNSS QoS were evaluated against GPS-based trajectories as ground truths. The results show that GNSS QoS-based routes provide routes with higher QoS, more than 50%, and longer, about 50%, than shortest routes.     

基于TransCAD的"一路一线"公交布线方法仿真研究

“一路一线”是近年来提出的一种公交布线新思路,目前还没有在实际中得以应用。为了验证“一路一线”公交布线方法的可行性,以佛山南海中心城区桂城为研究对象,运用仿真软件TransCAD建立起公交仿真系统。在对仿真对象公交线网现状进行仿真校验的基础上,再采用“一路一线”的公交布线方法重新设计其公交线网．进行仿真。为了评价“一路一线”公交布线方法的仿真效果,从设施水平和服务水平两个方面设定评价指标,分别对现状公交线网和采用“一路一线”方法布设的公交线网仿真的结果进行了比较、评价。该项研究对验证“一路一线”公交布线方法的可行性进行了有益探索,为城市公共交通的改善尤其是新兴城市公交线网的设计提供借鉴。     

欧盟摩托车防止非法改装指令的分析与研究(1)

通过对欧盟各国摩托车管理、驾驶执照和车辆税收制度以及非法改装技术的可行性、目的等方面进行综合分析和研究,全面掌握欧盟制定的防止非法改装指令的背景、缘由、目的、方法和要求,并结合目前可能存在的一些改装示例来分析摩托车行业的技术进步,提出了防止非法改装的其他控制措施及对适用车辆类型的扩展意见,以期对我国今后制订类似的标准能有借鉴意义。