Socioeconomic and usage characteristics of transportation network company (TNC) riders

Transportation - The widespread adoption of smartphones followed by an emergence of transportation network companies (TNC) have influenced the way individuals travel. The authors use the 2017...     

One city,three models: comparison of land‐use/transport policy simulation models for Dortmund

The paper reports on simulation experiments conducted by the International Study Group on Land‐Use/Transport Interaction (ISGLUTI) for the metropolitan region of Dortmund in the Federal Republic of Germany. Three land‐use/transport simulation models were applied to the Dortmund region: the DORTMUND model developed at the University of Dortmund, the LILT model being used at University College London and the MEPLAN package developed by Marcial Echenique & Partners in Cambridge. The three models are briefly characterized and their ex‐post forecasts are compared with the actual development of the region. The final section of the paper compares how the three models respond to a common set of assumptions and policies from the fields of land‐use control, traffic management and transport investment. The differences in model response give insights into the validity of the theoretical foundations and internal structure of the models.     

Public/private-sector cooperation in urban transportation: Lessons from ridesharing experiences in Connecticut

An important characteristic of urban transportation policy and planning today is the increasing role that the private sector is playing in identifying and implementing transportation projects. For example, a recent examination of the possible forms of such involvement found that there were four major categories of action that could be used to classify recent private-sector efforts in urban transportation: (1) aid to and/or provision of transportation services; (2) formation of advocacy or advisory groups whose purpose is to influence public policy; (3) sponsorship of transportation studies; and (4) provision of management assistance to public agencies (Gordon, 1982). In many of these efforts, the successful implementation of a project or program required close cooperation between public and private-sector officials. The purpose of this paper is to examine the characteristics of this interaction and explore the implications for transportation planning and policy.Examples of public/private-sector interaction in two Connecticut cities, Hartford and Stamford, are used to illustrate the characteristics of successful transportation program implementation. Although the examples are limited to two cities, and are mainly concerned with one major category of action (ridesharing), the characteristics of the process used and of the results can be applied to other situations where public/privatesector interaction is desired.     

Parking policy and urban goals: Linking strategy to needs

Parking management strategies have traditionally been used as a means of accommodating traffic demand, with little or no effort made to identify how such strategies might relate to other urban objectives. In this paper, parking management strategies are classified according to the control they exert over the amount of aggregate parking supply, access to parking, spatial distribution of parking supply, or dollar price of parking. Six general categories of urban policy objectives are identified, and the relationship between parking strategies and these objectives analyzed. The parking program in Baltimore is used to illustrate some of the relationships identified in this analysis. This paper concludes that the linkage between parking and the attainment of some urban objectives is potentially quite strong, and that further empirical research is needed to fully establish this relationship. Several different directions for further research are also identified.     

Aerodynamic design optimization of rear body shapes of a sedan for drag reduction

This study proposes an aerodynamically optimized outer shape of a sedan by using an Artificial Neural Network (ANN), which focused on modifying the rear body shapes of the sedan. To determine the optimization variables, the unsteady flow field around the sedan driving at very fast speeds was analyzed by CFD simulation, and fluctuations of the drag coefficient (C _D ) and pressure around the car were calculated. After consideration of the baseline result of CFD, 6 local parts from the end of the sedan were chosen as the design variables for optimization. Moreover, an ANN approximation model was established with 64 experimental points generated by the D-optimal methodology. As a result, an aerodynamically optimized shape for the rear end of the sedan in which the aerodynamic performance is improved by about 5.64% when compared to the baseline vehicle is proposed. Finally, it is expected that within the accepted range of shape modifications for a rear body, the aerodynamic performance of a sedan can be enhanced so that the fuel efficiency of the sedan can be improved. The YF SONATA, a sedan manufactured by Hyundai Motors Corporate, played a major role in this research as the baseline vehicle.     

Evasive manoeuvres with a steering robot

In the pursuit of an objective rating on vehicle stability performance, it is always desirable to reduce disturbances and inconsistencies during experimental evaluations, especially the ones introduced by human drivers. This paper presents the development of a steering robot designed for closed-loop steering tasks during evasive manoeuvres. It describes the controller structure and discusses experimental results, in addition to simulation/vehicle model verifications and theoretical control analysis.     

Method for obtaining the wheel–rail contact location and its application to the normal problem calculation through ‘CONTACT’

This work presents a robust methodology for calculating inter-penetration areas between railway wheel and rail surfaces, the profiles of which are defined by a series of points. The method allows general three-dimensional displacements of the wheelset to be considered, and its characteristics make it especially suitable for dynamic simulations where the wheel–rail contact is assumed to be flexible. The technique is based on the discretisation of the geometries of the surfaces in contact, considering the wheel as a set of truncated cones and the rail as points. By means of this approach, it is possible to reduce the problem to the calculation of the intersections between cones and lines, the solution for which has a closed-form expression. The method has been used in conjunction with the CONTACT algorithm in order to solve the static normal contact problem when the lateral displacement of the wheelset, its yaw angle and the vertical force applied in the wheelset centroid are prescribed. The results consist of smooth functions when the dependent coordinates are represented as a function of the independent ones, lacking the jump discontinuities that are present when a rigid contact model is adopted. Example results are shown and assessed for the normal contact problem for different lateral and yaw positions of the wheelset on the track.     

A tool to aid redesign of flexible transport services to increase efficiency in rural transport service provision

Rural areas generally have lower and more dispersed demands for travel which cannot sustain conventional public transport services and consequently have a greater number of flexible and demand responsive transport services operating. These services usually operate on a stand-alone basis, are often subsidized and are typically only accessible by certain passenger types or for specific trip purposes. This generally results in uncoordinated and inefficient transport provision overall. The Flexible integrated transport services (FITS) system featured in this paper has been designed to address this problem. FITS can be used as a planning tool to assess potential benefits from relaxing operating constraints (e.g., a service's operating boundaries), which can potentially suggest service redesign. It also includes the capacity to assign subsidy payments on a trip by trip basis to increase cost efficiency whilst meeting a greater proportion of transport needs. The case study in the paper focusses on transport to health in the Aberdeenshire and Morayshire areas of Scotland in the UK. Despite flexible transport operators receiving public funds to meet passenger needs, this is currently being supplemented by public bodies paying large amounts in taxi fares in instances where there is a statutory obligation to provide travel but where no other suitable transport service exists. The results demonstrate the potential substantial savings which could be realized by allowing transport operators to redesign their services by relaxing constraints and by the reassignment of subsidies: resulting in more passenger demands being met and a reduction in public spending on taxi fares.     

20世纪美国应对机动性的交通构想及高速公路发展历程

为了阐述20世纪除汽车机动性外,交通发展经历的最重要的进程——城市高速公路的出现,考察了过去100年来美国城市交通规划的历史。通过回顾各种研究资料,认为资助州际公路发展所采用的方法使联邦和州公路工程师成为主管,这影响了公路的选线及设计。联邦公路工程师只关注机动车通过效率的最大化,而在很大程度上忽略了城市的其他利害关系。没有先进的规划理念指导、过度建设、稀疏、放射环状的道路网对于加强机动性取得了极大的效益,但通常要为此付出巨大的社会和环境成本。最后指出,在实践中要重新审视具有百年历史的协调交通与土地利用规划的观点,而且,公共财政权宜之计式的政治决策方式将对工程、出行和城市形态产生深远的影响。·     

Biochemical composition of marine sediment from the eastern Weddell Sea (Antarctica): High nutritive value in a high benthic-biomass environment

Within the SCAR's international EASIZ programme, as part of the benthic–pelagic coupling experiment, grain size and organic matter contents in marine surface sediment were measured. Samples were taken during the austral autumn of 2000 from 3 regions in the eastern Weddell Sea: Kapp Norvegia, Four Seasons Bank, and Austasen.In general, sediments were fine sand with a grain size fraction < 200 μm representing more than 40% of the total weight. The sediments from Four Seasons Bank (64 to 107 m depth) were coarser than those from Austasen and Kapp Norvegia (209 to 480 m depth), presumably due to winnowing of fine sediment at shallow depths. Organic carbon (OC) content ranged from 0.25% to 1.2% and constituted 10% to 97% of the total carbon. The samples from Kapp Norvegia presented the highest OC values. Overall, protein (PRT), lipid (LPD), and carbohydrate (CHO) contents were similar to those in sediment from cold regions (e.g., the North Atlantic and the Ross Sea) but higher than those in sediment from other Antarctic and more septentrional regions (e.g., the Ross Sea and the Mediterranean). The difference within the Antarctic is explained through the local conditions in Terra Nova Bay and Kapp Norvegia. In the Antarctic, PRT and LPD carbon were the main contributors to the biopolymeric carbon (BPC). In the eastern Weddell Sea shelf, the BPC accounted for more than 90% of the OC in most of the samples. More than 82% of the total PRT, LPD, and CHO were present in the fraction < 200 μm. This work remarks the existence of sediments with a high nutritional value persistent several weeks after the spring–summer pulse of fresh organic matter. It is also highlighted the high potential availability of these sediments (due to its grain size) for the benthic communities inhabiting this high-latitude continental shelf.