Transport demand model estimation from traffic counts

Many problems in transport planning and management tasks require an origindestination (O-D) matrix to represent the travel pattern. However, O-D matrices obtained through a large scale survey such as home or roadside interviews, tend to be costly, labour intensive and time disruptive to trip makers. Therefore, the use of low cost and easily available data is particularly attractive.The need of low-cost methods to estimate current and future O-D matrices is even more valuable in developing countries because of the rapid changes in population, economic activity and land use. Models of transport demand have been used for many years to synthesize O-D matrices in study areas. A typical example of this is the gravity model; its functional form, plus the appropriate values for the parameters involved, is employed to produce acceptable matrices representing trip making behaviour for many trip purposes and time periods.The work reported in this paper has combined the advantages of acceptable travel demand models with the low cost and availability of traffic counts. Three types of demand models have been used: gravity (GR), opportunity (OP) and gravity-opportunity (GO) models. Three estimation methods have been developed to calibrate these models from traffic counts, namely: non-linear-least-squares (NLLS), weighted-non-linear-least-squares (WNLLS) and maximumlikelihood (ML).The 1978 Ripon (urban vehicle movement) survey was used to test these methods. They were found to perform satisfactorily since each calibrated model reproduced the observed O-D matrix fairly closely. The tests were carried out using two assignment techniques, all-or-nothing and the stochastic method due to Burrell, in determining the routes taken through the network.requests for offprints     

Self-Excited Vibrations of Railway Vehicle with Dry Friction Units

Some results obtained during developing a new approach to analysis of conditions of self-excitation of lateral vibrations of railway vehicles as systems of variable structure are given in this article. Structure variability is conditioned by the state of constraints with dry friction. An idea of the replacement of a nonlinear multibody system by a number of subsystems, which are linearized in a certain way, is worked out. The efficiency of the method suggested for the determination of the characteristics of self-excited vibrations of active multibody systems with dry friction is illustrated by way of an example of the investigation of the dynamic behaviour of a freight car.     

轨枕间距对钢轨波磨的影响

主要研究轨枕间距对钢轨波磨发展的影响。研究小半径曲线内轨的小矢跨比波磨。这些出现问题的曲线段属于西班牙毕尔巴鄂区域的地铁轨道,铺设着混凝土道床和两层STEDEF型支承垫层。当初始轨枕间距为1000mm时,仅有92万组轮对通过后所测得的波磨深度峰-峰值已经达到0.42mm。随后更换产生波磨的钢轨,比较列车通过时轨枕上方和轨间中部的内轨垂向、横向加速度。当轨枕间距为1000mm时,轨间中部出现频率为204和244Hz的强烈响应,在轨枕上方却未出现。在相邻轨枕中间铺设一个轨枕,使轨枕间距变为500mm,钢轨波磨停止发展。该结论是根据2年的观测结果得到的。     

Day-to-day variability in travellers’ activity-travel patterns in the Jakarta metropolitan area

Using four consecutive days of SITRAMP 2004 data from the Jakarta metropolitan area (JMA), Indonesia, this study examines the interactions between individuals’ activity-travel parameters, given the variability in their daily constraints, resources, land use and road network conditions. While there have been a significant number of studies into day-to-day variability in travel behaviour in developed countries, this issue is rarely examined in developing countries. The results show that some activity-travel parameter interactions are similar to those produced by travellers from developed countries, while others differ. Household and individual characteristics are the most significant variables influencing the interactions between activity-travel parameters. Different groups of travellers exhibit different trade-off mechanisms. Further analyses of the stability of activity-travel patterns across different days are also provided. Daily commuting time and regular work and study commitments heavily shape workers’ and students’ flexibility in arranging their travel time and out-of-home time budget, leading to more stable daily activity-travel patterns than non-workers.     

Measuring the impacts of weather variability on home-based trip chaining behaviour: a focus on spatial heterogeneity

Using the 2011 Swedish national travel survey data, this paper explores the influence of weather characteristics on individuals’ home-based trip chaining complexity. A series of panel mixed ordered Probit models are estimated to examine the influence of individual/household social demographics, land use characteristics, and weather characteristics on individuals’ home-based trip chaining complexity. A thermal index, the universal thermal climate index (UTCI), is used in this study instead of using directly measured weather variables in order to better approximate the effects of the thermal environment. The effects of UTCI are segmented into different seasons to account for the seasonal difference of UTCI effects. Moreover, a spatial expansion method is applied to allow the impacts of UTCI to vary across geographical locations, as individuals in different regions have different weather/climate adaptions. The effects of weather are examined in subsistence, routine, and discretionary trip chains. The results reveal that the ‘ground covered with snow’ condition is the most influential factor on the number of trips chained per trip chain among all other weather factors. The variation of UTCI significantly influences trip chaining complexity in autumn but not in spring and winter. The routine trip chains are found to be most elastic towards the variation of UTCI. The marginal effects of UTCI on the expected number of trips per routine trip chain have considerable spatial variations, while these spatial trends of UTCI effects are found to be not consistent over seasons.     

Transit service quality analysis using cluster analysis and decision trees: a step forward to personalized marketing in public transportation

A transit service quality study based on cluster analysis was performed to extract detailed customer profiles sharing similar appraisals concerning the service. This approach made it possible to detect specific requirements and needs regarding the quality of service and to personalize the marketing strategy. Data from various customer satisfaction surveys conducted by the Transport Consortium of Granada (Spain) were analyzed to distinguish these groups; a decision tree methodology was used to identify the most important service quality attributes influencing passengers’ overall evaluations. Cluster analysis identified four groups of passengers. Comparisons using decision trees among the overall sample of all users and the different groups of passengers identified by cluster analysis led to the discovery of differences in the key attributes encompassed by perceived quality.     

Modelling bicycle use intention: the role of perceptions

Users’ perceptions are identified as key elements to understand bicycle use, whose election cannot be explained with usual mobility variables and socio-economic characteristics. A hybrid model is proposed to model the intention of bicycle use; it combines a structural equations model that captures intentions and a choice model. The framework is applied to a case of a university campus in Madrid that is studying a new internal bike system. Results show that four latent variables (convenience, pro-bike, physical determinants and external restrictions) help explaining intention to use bike, representing a number of factors that are linked to individual perceptions.     

地铁曲线段不规则磨耗引起的钢轨波磨监测

在小半径曲线的内轨侧出现钢轨短波波磨加剧的现象,是世界上许多铁路网都面临的一个问题。由于地铁线路小半径曲线大量存在,受其影响尤为突出。本文为一实例研究,属于一个研发预测曲线地段钢轨波磨的数值工具课题的一部分。在斯德哥尔摩地铁中一处半径为120m的曲线段上,通过重复测试轨道的粗糙度及列车通过时引起的噪声,监测波磨的发展状况。在一年的打磨过程中,发生了剧烈的短波波磨,最大峰-峰值约为0.15mm。测试数据谱分析显示,在4～14cm波长范围内,粗糙度幅值较大,峰值约在5和8cm处。波磨为单一的纵向形式（波峰与轨道方向垂直）,幅值在100m长的被测轨道段上呈现不规则变化。粗糙度增长速率随时间增加,直至钢轨打磨后的300天,此后仅有少量的附加粗糙度出现。由于平均车速约为30km/h,因此由波磨造成的滚动噪声主要处于200Hz以下的低频段。打磨后的139～300天,4～14cm波长范围内粗糙度级增加10.1dB,与之相应的60～200Hz频段内的滚动噪声级增加4.9dB。在干燥天气条件下,列车通过时引起人体不适的噪声主要是车轮啸鸣噪声而非滚动噪声。     

Simulation of vertical dynamic vehicle–track interaction using a two-dimensional slab track model

The vertical dynamic interaction between a railway vehicle and a slab track is simulated in the time domain using an extended state-space vector approach in combination with a complex-valued modal superposition technique for the linear, time-invariant and two-dimensional track model. Wheel–rail contact forces, bending moments in the concrete panel and load distributions on the supporting foundation are evaluated. Two generic slab track models including one or two layers of concrete slabs are presented. The upper layer containing the discrete slab panels is described by decoupled beams of finite length, while the lower layer is a continuous beam. Both the rail and concrete layers are modelled using Rayleigh–Timoshenko beam theory. Rail receptances for the two slab track models are compared with the receptance of a traditional ballasted track. The described procedure is demonstrated by two application examples involving: (i) the periodic response due to the rail seat passing frequency as influenced by the vehicle speed and a foundation stiffness gradient and (ii) the transient response due to a local rail irregularity (dipped welded joint).