Simulating Demand-responsive Transportation: A Review of Agent-based Approaches

Abstract

In light of the need to make better use of existing transport infrastructure, demand-responsive transportation (DRT) systems are gaining traction internationally. However, many systems fail due to poor implementation, planning, and marketing. Being able to realistically simulate a system to evaluate its viability before implementation is important. This review investigates the application of agent-based simulation for studying DRT. We identify that existing simulations are strongly focused on the optimisation of trips, usually in favour of the operator, and rarely consider individual preferences and needs. Agent-based simulations, however, permit incorporation of the latter, as well as capture the interactions between operators and customers. Several areas of future research are identified in order to unify future research efforts.     

Road Safety Trends at National Level in Europe: A Review of Time-series Analysis Performed during the Period 2000–12

Abstract

This paper presents a review of time-series analysis of road safety trends, aggregated at a national level, which has been performed in the period 2000–12 and applied to European national data sets covering long time periods. It provides a guideline and set of best practices in the area of time-series modelling and identifies the latest methods and applications of national road safety trend analysis in Europe. The paper begins with the methodological framework adopted for aggregate time-series modelling that will be considered, and then discusses a number of relevant applications to long-period data aggregated at the national level, whether for countries alone, or for groups of countries. Some analyses, which were performed at the disaggregated level, are also provided, as they are being used more and more. Finally, the paper summarizes and discusses the significant changes in aggregate road safety trend analysis which occurred during the period and provides recommendations for continuing these research efforts.     

A tool for calculating aircraft emissions and its application to Greek airspace

This paper quantifies the impact of aircraft emissions on local air quality and climate change. Aircraft emissions during the cruise cycle and the landing/take-off cycle are considered. A tool is developed that computes emission values using real-time air traffic data derived from various databases. Emissions include carbon dioxide, hydrocarbons, carbon monoxide and nitrogen oxides. The overall output is a detailed ‘emissions map’ of a given territory that enables the identification of critical emission spots including routes, airports, season, aircraft type and flight category. The method can be used for real-time monitoring of airline emissions and for policy analysis. The proposed tool and resulting outputs are illustrated in the case of the Greek airport system using domestic, international and overflights. Demand volatility driven mainly by tourism and its impact on emissions is assessed.     

Campus parking supply impacts on transportation mode choice

Parking demand is a significant land-use problem in campus planning. The parking policies of universities and large corporations with facilities located in small urban areas shape the character of their campuses. These facilities will benefit from a simplified methodology to study the effects of parking availability on transportation mode mix and impacts on recruitment and staffing policies. This paper, based on a case study of North Dakota State University in the United States, introduces an analytical framework to provide planners with insights about how parking supply and demand affects campus transportation mode choice. The methodology relies only on aggregate mode choice data for the special generator zone and the average aggregate volume/capacity ratio projections for all external routes that access the zone. This reduced data requirement significantly lowers analysis cost and obviates the need for specialized modelling software and spatial network analysis tools. Results illustrate that the framework is effective for analysing mode choice changes under different scenarios of parking supply and population growth.     

钢桁连续刚构桥模型简化方案

特大桥梁模型试验规模较大,制作、测试均较复杂,因此,需要在尽可能反映实桥真实应力的情况下简化试验模型。通过不同模型方案计算分析后得知,在一定的边界条件下,钢桁连续刚构桥全桥一半模型完全能够真实地反映实桥受力状态。这样就能将模型所需的资源减小一半,而且可以在有限的试验室空间内将模型尺寸相对做大。     

潍坊寿光港区航道工程防沙堤平面布置形式研究

采用波浪潮流泥沙数学模型试验手段,对潍坊寿光港区防沙堤建设中的平面布置形式进行研究。根据研究成果,建议选择北槽航道作为5 000 t级通海航道,航道走向63.5°~243.5°。防沙堤工程建议采用双导堤形式,其中北导堤应接岸。建议堤头可先达-4.0 m水深处,观测其堤头附近冲淤变化后,再决定是否继续向海延伸。     

盾构隧道施工对富水软弱地层的扰动分析

为研究盾构隧道施工对富水软弱底层的扰动影响,以大连地铁某标段盾构隧道施工为例,首先基于修正剑桥模型建立土体本构关系,利用Shell结构单元模拟盾构初衬;然后采用流固耦合方法研究土体固结过程对盾构开挖引起软弱地层扰动问题;最后根据仿真结果与现场实测数据,绘制地表沉降对比分析曲线,给出盾构施工引起地表沉降的动态变化趋势.结果表明：孔隙水在盾构开挖完成后仍持续向隧道方向渗透,并引起距隧道较近区域的扰动趋势大于周围较远区域.本研究对提高富水软弱地层条件下盾构施工过程建模的准确性和实效性、指导盾构施工具有指导作用.     

剪纸艺术之审美意蕴及其在现代平面设计的运用

剪纸艺术是一株灿烂的民族艺术之花,是活态的生活文化史,具有深厚而丰赡的审美意蕴。文章通过分析剪纸艺术的风格特征,将其与现代平面设计相结合。重点从传统与现代、传承与创新、图形与设计三个方面,论述了剪纸艺术在现代平面设计中的新理念。通过实例分析可知,二者的巧妙结合,是借鉴其形式特点,保留其形式遗风,借用、延伸其寓意,并结合现代设计理念和表现手法,对其进行再设计,赋予其时代气息和新的生命力。     

大跨度拱桥变截面吊杆索力的分析与识别

上海亭枫公路跨平申线航道的三跨30 m+120 m+30 m连续钢桁架拱桥采用变截面吊杆，其施工过程索力的准确识别具有一定的技术难度，需要有效的理论分析结合实际工程经验来解决。利用等截面吊杆索力的计算公式，结合SAP2000变截面吊杆有限元模型的参数分析结果，推导出不同规格的吊杆基准等效长度。根据吊杆基准等效长度和实测频率，采用一端固定、一端铰接的索力计算公式计算索力，并与相应阶段的设计索力进行比较，可以得到主桥吊杆索力基本符合设计要求。     

Numerical simulation of piggyback pipelaying under current loadings

For piggyback pipelaying operations, current-induced force and its effect on the piggyback pipe have not been thoroughly studied. In the present study, an improved method in hydrodynamic load calculation and structural modelling is proposed to simulate the pipelaying of a piggyback pipeline. In order to obtain the mean drag and lift force coefficients for the piggyback pipeline subjected to different inflow angles, two-dimensional Computational Fluid Dynamics (CFD) simulations are performed by modelling the piggyback pipeline as two cylinders attached to each other without gap. Then, the acquired force coefficients are used to calculate the hydrodynamic loads through a user-defined function in OrcaFlex based on a cross-flow principle approach. The interaction between the pipeline and the piggyback cable is modelled using two types contact elements which are ring penetrator and non-penetrating contact. The present proposed method is compared with other two widely used engineering methods based on (1) the equivalent diameter and (2) two separate cylinders without accounting for hydrodynamic interaction, in terms of the top tension, and the bending moments at Hang-off Clamps (HOC) and sagbend of the pipeline. The comparison shows that the two widely used engineering methods are not always conservative in force and response predictions. Hence, it is important to consider the hydrodynamic and structural interactions between the piggyback cable and the pipeline. With different current directions, the bending moments at the HOC predicted by the present method vary from 40% lower to 100% higher than those predicted by the two widely used engineering methods.