基于权的最小平方法的山区道路交通安全度模糊综合评价

针对山区道路交通特点,综合考虑影响山区道路交通安全度的人、车、路、环境等主要因素,运用层析分析法构建道路交通安全度评价指标体系,基于权的最小平方法建立模糊综合评价模型,并利用加权平均原则对其进行综合评价.以云南省罗富路"者桑"段为例,结果表明该模型可以有效的反映道路的安全状况,且权的最小平方法可以实现道路交通安全度主要影响因素权重系数的精确分配,合理反映各评价指标的重要性,为提高道路的交通安全性奠定基础.     

关于圆形和方形城市工作区道路交通面积的解析与比较

对于城市规划来讲，事先预测其工作区内所需道路面积，以尽量避免实际交通网络中发生拥挤阻塞，具有重要意义，在本文，我们通过考虑一个城市通勤高峰时期的车辆交通情况，并通过利用走行中的车辆占用道路面积这一概念，基于一个相对现实的模型，从理论上对圆形方形城市工作区推导了所需的道路面积，并将两者加以比较，以发现与其交通网络结构相关的工作区的相对有效形状。     

Mathematical models for motion of the rear ends of vehicles

A new treatment of the path of the rear wheels of single and multiple axle vehicles produces simple first order differential equations for the motion of the rear wheels relative to the front wheels. We show for the first time, under the assumption of no slipping, that the path of the rear wheels depends only on the path of the front wheels and not on the vehicle speed. We examine motion along straight, circular and winding roads, giving closed form solutions in the first two cases. We also provide a straightforward algorithm for computing vehicle offtracking for any road geometry. We believe these results will be of significant benefit to road designers.     

基于畅通可靠性的开放小区交通流分配及优化决策

开放小区内部道路可增加城市道路网的密度和可达性,从而达到缓解城市道路拥堵的目的。通过对出行者进行问卷调查,得知其路径选择行为主要考虑出行时间及时间波动性两方面因素,基于此对CONTRAM费用函数进行改进,得到适用于小区开放后的广义出行费用,该费用考虑了畅通可靠性对路径选择的影响;结合小区开放后出行者选择准则,建立考虑广义出行费用的随机用户最优模型(SUO),并采用逐次平均算法(MSA)进行求解,从而得到更为精确的路段交通流量;基于小区道路开放后需承担的交通量,结合城市道路规划相关规范,对横断面、出入口等方面提出开放小区内部道路规划的建议。     

基于SD-VF理论的城市限行政策效应研究

随着我国城市化进程不断加快,城市交通供需矛盾日益突出,交通拥堵问题愈发严重,我国各地纷纷实行各种政策措施来缓解交通拥堵。本文以北京市为例,针对城市交通拥堵的现象,从系统的角度出发,运用系统动力学与灰色Verhulst预测相结合的方法(SD-VF),建立城市交通治堵模型,并采用Vensim软件对模型进行动态仿真分析,从经济、社会、环境等方面探究政策措施对城市环境生态承载力、道路生态承载力等的影响。研究结果表明,限行限号政策虽然在一定程度上提高道路生态承载力,但也可能引发“悖论”效应;修路政策并没有根本上解决城市交通拥堵问题,仅仅是把拥堵状况向后推迟;而相对于单一政策,将发展公共交通与限行政策相结合可以有效缓解交通拥堵,改善空气质量,提升环境承载力,是更加科学合理的政策措施。     

Evaluation of a new maintenance concept for the preservation of highways

Asphalt roads gradually deteriorate over time and need mendingto remain in a good state. Inspections are performed to obtaininformation about the current state of the road; when the levelof damage reaches the established standards, the road is repairedthrough a maintenance action that is considered most cost-effective.Because of economies of scale, it is to a certain extent economicalto limit the number of maintenance services by integrating neighbouringsegments into a homogeneous section which is completely repaired.In this report we consider the question of whether it is economicallyjustified to adopt a maintenance concept in which the road isoccasionally regenerated from junction to junction with a distanceof several kilometers. The big advantage of junction-to-junctionmaintenance is that it can be done within special road barrierconstructions which reduce the road capacity only slightly,so that the road can be maintained 24 hours a day.     

Optimal hierarchical system of a grid road network

This paper develops a simple analytical model for determining the hierarchical system of road networks. The model is based on a grid road network where roads are classified into three types according to road widths and travel speeds. We derive the optimal ratios of road areas that minimize the average and maximum travel time. Minimizing the average travel time provides an efficient solution, whereas minimizing the maximum travel time provides an equitable solution. Both of the solutions are expressed in terms of road widths and travel speeds. As an application of the grid network model, we evaluate the hierarchical system of the road network of Tokyo.     

On Dynamic Aspects and Pattern Generation in Vehicle-Road Interaction

Increasing transport capacity leads to new vehicle designs and increasing axle loads. Still it has to be better understood until which extend especially heavy vehicles cause corrugation of roads. Therefore, basic investigations concerning vehicle-road interaction are helpful to augment the understanding of the basic mechanisms. Firstly, in order to investigate the oscillatory behavior of a vehicle a MDoF oscillator moving with constant velocity on a rippled road is considered. From this, general results about wear pattern generation of the road are derived from analytical considerations concerning the dynamic contact force between vehicle and road. Secondly, a simple vehicle road interaction model is presented which consists of a vehicle model and a road exhibiting viscoelastic plastic characteristics. Results of numerical simulations are compared with the findings deduced from the analytical MDoF model. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new harvest operation cost model to evaluate forest harvest layout alternatives

In this paper we develop a new model for harvest operation costs that can be used to evaluate stands for potential harvest. The model is based on felling, extraction, and access costs and is unique in its consideration of the interaction between harvest area shapes and access roads. We illustrate the model and evaluate the impact of stand size, volume, and road cost when determining harvest layouts. We also present a generalized case where multiple unit road costs are considered in the same stand.     

An Interactive Algorithm for Vehicle Routeing for Winter — Gritting

In winter, when roads may become dangerously slippery due to frost, ice or snow, a de-icing agent (usually salt) is spread on them by a local authority for safety reasons. A gritter only needs to travel once down all those roads requiring treatment, as it can spread the salt onto both sides of the carriageway. The problem studied is how to design routes for gritters which will minimise costs. This problem is a type of Capacitated Arc Routeing Problem including consideration of multiple depot locations, limited vehicle capacities, time constraints on when roads must be gritted, roads with different priorities for gritting, the existence of one-way roads and salt-refilling locations. The objective function to be optimised depends on both the total distance travelled and the number and capacity of the gritters. A heuristic algorithm is devised with a computer program which allows user-interaction, and provides a practical tool for planning gritter routes. The model is linked to a GIS containing information on the road network for the County of Lancashire. Test results from the interactive algorithm are found to outperform another existing approach which solves the same problem.     

The periodic capacitated arc routing problem with irregular services

The aim of this paper is to introduce the periodic capacitated arc routing problem with irregular services. Some applications can be found in road maintenance operations and road network surveillance. The problem consists of determining a set of routes to cover a given network over a time horizon. The roads must be serviced a number of times in sub-periods over the time horizon, according to a hierarchy of arc classes. We present a mathematical model and a heuristic solution approach.     

Optimal control of road freight flows by route choice inducement: A case from Mexico

Contrasting with much of the research in freight transportation around the impacts to transport operators, this work focuses on the Road Planner providing the infrastructure. This viewpoint, seeking minimal repair costs and other payments generally conflicts with the carriers’ view, looking for the best hauling route.On a random utility frame, the user-planner interaction is modelled on a partially tolled road network, considering two types of costs: (a) lorries’ trip cost guiding the route choice, and affected by planners’ actions, and (b) planners’ road repair costs, depending on the traffic, the vehicles’ type and the control implementation. A Monte Carlo simulation bases the stochastic assignment on the network, determining optimal subsidies that divert traffic to tolled roads. On a portion of the Mexican Paved network optimal subsidies are found, increasing the toll roads’ use and reducing traffic on the non-charged roads, generally having weaker pavements and higher maintenance costs.     

Traffic flow optimization on roundabouts

The aim of this article is to propose an optimization strategy for traffic flowon roundabouts using amacroscopic approach. The roundabout is modeled as a sequence of 2 × 2 junctions with one main lane and secondary incoming and outgoing roads. We consider two cost functionals: the total travel time and the total waiting time, which give an estimate of the time spent by drivers on the network section. These cost functionals areminimized with respect to the right ofway parameter of the incoming roads. For each cost functional, the analytical expression is given for each junction. We then solve numerically the optimization problem and show some numerical results. Copyright © 2014 John Wiley & Sons, Ltd.     

Transverse vibration of nonhomogeneous orthotropic viscoelastic circular plate of varying parabolic thickness

An analysis of the transverse vibration of nonhomogeneous orthotropic viscoelastic circular plates of parabolically varying thickness in the radial direction is presented. The thickness of a circular plate varies parabolically in a radial direction. For nonhomogeneity of the circular plate material, density is assumed to vary linearly in a radial direction. This paper used the method of separation of variables in solving the governing differential equation. In this paper, an approximate but quite convenient frequency equation is derived by using the Rayleigh–Ritz technique with a two‐term deflection function. Deflection, time period and logarithmic decrement for the first two modes of vibration are computed for the nonhomogeneous orthotropic viscoelastic circular plates of varying parabolic thickness with clamped edge conditions for various values of nonhomogeneity constants and taper constants and these are shown in tabular form for the Voigt–Kelvin model. Copyright © 2011 John Wiley & Sons, Ltd.     

不同行为风格下路段行人与机动车行为博弈分析

针对路段过街行人与机动车的博弈决策行为,考虑不同交通行为风格下行人的过街特征和驾驶人的驾驶行为习惯等影响因素,开展路段行人交通行为风格调查,掌握不同交通行为风格下路段行人的过街特征,构建非合作动态人车博弈模型.通过分析不同策略下行人与驾驶人的收益,求解纳什均衡,得到不同策略下行人与驾驶人的最优策略.为解决路段行人与机动车冲突提供新的思路.     

Traffic queue estimation

This paper deals with the urban traffic queue modelling and estimation. A general formulation of delays on a road section is used to link measured speeds at its entrance to the current queue state. This measurement model is applied to correct a posteriori the queue state distribution whose a priori evolution is ruled by a time varying Markov chain. The resulting predictor-corrector is tested with a microscopic simulation tool. Results in fixed plan control show that for long road sections (200 meters) the estimation error is unacceptable whereas for short road sections (50–100 meters) the average quadratic error is about 1 vehicle². In real time control conditions, in spite of a significant increase of the estimation quadratic error, results show a delay benefit of 15% with respect to the fixed plan control.     

Traffic flow modelling with junctions

Motivated by the modelling of a roundabout, we are led to study the traffic on a road with points of entry and exit. In this note, we would like to describe the modellisation of a junction and solve the Riemann problem for such a model. More precisely, between each point of discontinuity we use a multi-class extension of the LWR model to describe the evolution of the density of the vehicles, the ‘multi-class’ approach being used in order to distinguish the vehicles after their origin and destination. Then, we treat the points of entry and exit thanks to special boundary conditions that give bounds on the flows of the different types of vehicles. In the case of the one-T road we obtain a result of existence and uniqueness. This first step allows us to obtain a similar result for the n-T road. We describe these results and also some properties of the obtained solutions, in order to see how long this model is valid.     

夹层圆板轴对称非线性弯曲和屈曲的样条函数解法

以三次B样条函数为试函数,用配点法计算夹层圆板的非线性弯曲．支座可以是弹性的．夹层板采用Reissner模型．荷载可为多项式型的分布荷载、均布边缘力矩、均布径向压力或均布径向预应力及它们的组合．首次用非线性理论计算了夹层圆板的压曲临界荷载．在均布荷载作用下的结果同幂级数解的结果作了比较,说明样条配点法具有收敛范围大、精度高、编写程序通用的优点．     

Distributions for Gaps in Road Traffic

The importance of both counting and gap distributions in roadtraffic flow has been recognized for some years. One reasonfor their importance is that they are linked to three importantaspects of road traffic viz. flow, concentration and capacity.The flow-rate is the reciprocal of the mean time-gap betweenvehicles and concentration is the reciprocal of the mean distance-gapbetween vehicles. Capacity is, in one sense or another, themaximum flow, and is thus related to the minimum time-gap betweenvehicles. Another reason for the importance of these distributionsis that the distribution of vehicles on a road can be consideredas a succession of moving gaps and dealt with on that basis. The displaced exponential distribution has been known for sometime to be a reasonably good model for low-medium flow-ratesof up to about 800 vehicles per hour (v/h) in one lane, butit breaks down for higher flows. A number of alternatives tothe displaced exponential are considered in this paper. A substantial amount of data, collected in New Zealand, hasbeen used in fitting the distributions. There is no real evidenceto show that the displaced exponential can be improved uponmuch as a model, although overall the use of a mixed exponentialimproves the fit somewhat. However, all the alternative distributionsare easy to sample from, and can be used in simulation studies.     

Analytic solutions of a reducible strain gradient elasticity model for solid cylinder with a cavity and its application in zonal failure

In this work, the reducibility condition of the fourth-order equilibrium equation in the strain gradient elasticity (SGE) model for solid cylinder with a cavity is obtained. When the reducibility condition is satisfied, the analytic displacement, generalized radial stress, and generalized angular stress can be solved out, and according to the higher-order coefficients, internal length scale, and Lamé constants, the displacement, generalized radial stress, and generalized angular stress are classified into four types: (1) conventional elasticity solution, (2) quasiperiodic SGE solution, (3) monotonous SGE solution, and (4) non-real-number solution. Quasiperiodic generalized radial stress and generalized angular stress are used to explain the occurrence of zonal failure of surrounding rock of a circular roadway. Numerical analysis with MATLAB is applied to study the influence of loading on zonal failure of surrounding rock of a circular raodway.