A multi-level spatial-temporal model for freight movement: The case of manufactured goods flows on the U.S. highway networks

The spatial production, attraction, and movement of manufactured goods are vital to the economy of a region and country. The U.S. department of transportation also mandates to incorporate continuing and efficient freight movement and infrastructure into statewide and local long range planning. Studies on supply, demand, and transport of manufactured goods by firm, industry, mode, or commodity are vast in the logistics and supply chain literature. However, relatively sparse research is available on aggregated movement or freight on national, state, or local transportation networks. Better understanding and modeling freight movement on highway networks to facilitate local transportation, land use, economic development, and comprehensive planning is at the heart of freight research. Therefore, the major endeavors and novel contributions of this research include a conceptual framework proposed for freight movement research, a multi-level spatial-temporal freight model based upon the social optimum assignment for optimal “from”, “to”, “within”, and “through” freight flows of manufactured goods on the U.S. highway networks, and a set of performance measures designed to reveal states in terms of their competitive advantages in production, attraction, self-sufficiency, or cross-road. The freight flows were first visualized and highlighted by state at the U.S. level, then by county at the state level for Oklahoma, and finally by traffic analysis zone for the Tulsa metropolitan area. The spatial split of freight flows was accomplished through using freight, network, and demographic-economic databases at state, county, and zone scales.     

我国铁路货运需求结构的VAR模型分析

在建立铁路货运量、国民经济、铁路网扩展的协整VAR模型基础上,分析三者之间的长期均衡关系和短期动态关系。结果表明,在长期中,铁路货运量随国民经济增长呈缓慢增长趋势,而随铁路网扩展呈较快增长趋势。在短期中,国民经济是铁路货运量的重要影响因素;铁路货运量和铁路网扩展对国民经济影响不大;铁路货运量是铁路网扩展的重要影响因素,而国民经济变化对其影响不大。     

小交通量路网改造资金优化投资模型的研究

传统的以经济效益为目标函数的优化模型在一定程度上影响了路网改造项目决策的合理性.针对我国西部地区经济落后、交通量小、客货在途时间价值低的特性,采用以道路服务水平提高值作为目标函数,资金投入作为约束条件的优化模型,对西部路网改造资金进行了优化分配.该模型在湖北省恩施地区的路网改造资金优化中取得良好效果.     

The geography of freight-related accidents in the era of E-commerce: Evidence from the Los Angeles metropolitan area

Due to the burgeoning demand for freight movement in the era of e-commerce, freight related road safety threats have been growing in both urban and suburban areas, despite the improved general traffic safety over the past decades. The empirical evidence on how freight trucks related crashes are distributed across neighborhoods and correlated to spatially varying factors is, however, highly limited. This article uses data from the Los Angeles region in 2018 to analyze the spatial patterns of freight trucks related traffic crashes and examines the major factors that contribute to those patterns using spatial econometric models. Maps show that freight trucks related crashes are highly associated with major freight generators but less clustered than the overall traffic crashes. Results from the spatial Durbin model indicate that access to freight generators, economic attributes, land uses, road infrastructure, and road network variables all contribute to the spatial distribution of freight trucks related crashes. The findings could help transport planners understand the dynamics of freight trucks related traffic safety and develop operational measures for mitigating the impacts of growing goods movement on local communities.     

An inventory-based simulation model for annual-to-daily temporal freight assignment

In the aggregate freight demand modeling literature, temporal assignment (annual to daily flows) is often oversimplified or neglected altogether. Unlike passenger flows, freight flows over the course of a year are not uniform and can vary significantly as the result of trade-offs between inventory and transportation cost management. We introduce the first temporal assignment model that explicitly considers these trade-offs for aggregate freight forecasting. A two-stage model is proposed that first decomposes aggregate annual zonal flows to firm group annual flows using a supply chain network model, which are then temporally assigned by simulating purchase order transactions throughout supply chains. Lot sizes are estimated with an Economic Order Quantity (EOQ) model and calibrated with monthly inventory data. The result is an aggregate-disaggregate-aggregate model that fits into aggregate freight forecasting models but makes use of more disaggregate logistical data. The model is illustrated with a simple replicable example, followed by a case study conducted with California statewide data to break out the distributed zonal flows into average daily volumes for network assignment. Calibration results using 2007 IMPLAN data showed a median percentage difference of simulated annual flows from FAF³ data of 2.38%, and a median percentage difference of simulated inventories from IMPLAN data of 4.85%, which suggests an excellent fit. Empirical validation results showed the model outperforms fixed factor approaches in mean value accuracy by 15–31%.     

Performance measurement of a transportation network with a downtown space reservation system: A network-DEA approach

We propose an evaluation approach for a novel travel demand management strategy known as the downtown space reservation system (DSRS). This approach takes into account three perspectives, i.e., transportation service provider’s, the user’s, and the community’s and is based on network-Data Envelopment Analysis (DEA) where the perspectives are inter-related through intermediate inputs/outputs. Two types of network-DEA models (radial and slacks-based models) are considered. An example is provided using data propagated from a microscopic traffic simulation model of the DSRS. The results show that individual node performance can drive network DEA performance and that this information can inform future designs of the DSRS.     

Long haul freight network design using shipper–carrier freight flow prediction: A California network improvement case study

Transportation network design is a method for analyzing the interactive benefits of transportation projects applied to a network. In this paper, a network design model is developed for long haul freight movements which are represented by relationships between shippers and carriers. Additionally, an explicit capacity constraint is used to divert traffic volume from congested links. A case study based on the California transportation network is implemented to examine the effectiveness of this model when applied to a large network. A geographic information system is used to facilitate data management and analysis of the results.     

Urban spatial structure,employment subcenters,and freight travel

Metropolitan areas in the U.S. have become increasingly polycentric. Large employment subcenters have emerged outside of central cities, competing against the traditional city center for labor and businesses. The existing literature on land use and transportation focuses on passenger travel, providing little insight into the impact of polycentric metropolitan development patterns on freight activity. In this study, we use the Los Angeles region as a case study to examine the relationship between urban spatial development patterns and freight travel. Using the National Employment Time Series (NETS) data, we identify employment subcenters in metropolitan Los Angeles. We characterize freight activities associated with the subcenters using data from the Southern California Association of Governments (SCAG). We develop a regression model that estimates freight activity as a function of geographic characteristics, such as whether a location is in an employment subcenter, measures of nearby employment, access to the highway network, and proximity to intermodal freight facilities. The results indicate that employment is an important driver of freight activity; however, employment subcenters have an independent effect on freight activity. The results of this study suggest that further research on urban spatial structure and freight activity should assess the effects of employment subcenters and how their particular employment composition and characteristics are associated with freight activities at the metropolitan level. Such an approach would lead to more precise policy recommendations for urban goods movement.     

新建铁路项目分流运量计算方法研究

根据铁路运输的特点,把新建铁路项目所承担的客货运输量的交流范围划为项目的影响范围,结合影响范围内的客货OD流和相关径路表,分析借鉴公路交通量配流模型,提出新建铁路项目分流运量计算方法,并举例说明其应用。     

竞争性综合运输中公路货运定价的研究

利用双层优化方法,将公路货运企业的经营目标函数和客户的选择函数统一考虑,分析了在客户选择最优基础上的公路货运定价问题,通过构建模型,求解得到货运价格。该价格是满足消费者福利剩余最大化的价格,有利于社会资源的优化配置和公路货运企业、综合运输市场的发展。     

基于广义回归神经网络的铁路货运量预测

针对BP神经网络预测存在局部极小缺陷和收敛速度慢的问题,提出基于广义回归神经网络(GRNN)的预测模型。基于我国1999—2008年铁路货运量的历史统计数据,应用GRNN模型和混沌BP神经网络模型对铁路货运量进行预测。通过两种预测模型的计算结果比较说明,GRNN模型具有良好的收敛性和较高的精度,而且模型结构简单、计算速度快,具有良好的实用性。     

Spatial impact analysis of trans-Yangtze highway fixed links: A case study of the Yangtze River Delta,China

As an important infrastructure connecting straits or rivers, the construction of fixed links has become an effective measure for improving traffic conditions and promoting socio-economic development in many countries and regions around the world. Thus, it has become a significant topic in the field of transport geography. Taking the Yangtze River Delta as its case area, this study proposes a spatial impact model of trans-Yangtze highway fixed links, consisting of three components: an accessibility model, modified gravity model, and traffic utilisation model, which are used to analyse, respectively, cross-Yangtze accessibility and changes to transport structure, cross-Yangtze urban interaction and changes to economic structure, and the utilisation relationship of fixed links. Making use of existing fixed links while planning and building new ones has become the basis for achieving regional integration and sub-regional cooperation in this area, the aim of which is to create the barrier-free circulation of elements. The results prove that this spatial impact model coincides with reality. The increase in the number of fixed links has significantly shortened cross-river travel time and facilitated a unification of north-south highway networks. It has also promoted the formation of a high-connection urban network along the river. Northern urban nodes have joined the southern economic circle and finally achieved north-south integration. There are complex relationships between fixed links and their hinterlands, showing obvious utilisation gaps between the links. The complete system of trans-Yangtze fixed links is comprised of several river crossing facilities and connected highways. The function of each link is related to its role in the regional highway network. From a small number of fixed links to the realisation of multiple trans-Yangtze bridges and tunnels with easy access to multiple arterial highways, a ‘many-to-many’ spatial pattern is created that ultimately leads to the evolution of regional transport and economic structures.     

A delay estimation technique for single and double-track railroads

To route and schedule trains over a large complex network can be computationally intensive. One way to reduce complexity could be to “aggregate” suitable sections of a network. In this paper, we present a simulation-based technique to generate delay estimates over track segments as a function of traffic conditions, as well as network topology. We test our technique by comparing the delay estimates obtained for a network in Los Angeles with the delays obtained from the simulation model developed by Lu et al. [Lu, Q., Dessouky, M.M., Leachman, R.C., 2004. Modeling of train movements through complex networks. ACM Transactions on Modeling and Computer Simulation 14, 48–75], which has been shown to be representative of the real-world delay values. Railway dispatchers could route and schedule freight trains over large networks by using our technique to estimate delay across aggregated network sections.     

Demand forecast,congestion charge and economic benefit of an automated highway network for the paris agglomeration

This article is based on the main results of a pre-doctoral dissertation (DEA) on transport done at the ENPC. The research is about an economic evaluation of an automated highway network in the Paris urban agglomeration in the Ile de France Region.To this end, an automatic highway network incorporated into the road network in Ile de France has been modelled by means of the AEL-Davis software. Moreover, a congestion charging system has been introduced in the modelling. The targeted date of this study is 2020 so projections of a demand for alternative car commuting were made for that period. In addition the phenomena of total generation were taken into account in the evaluation. In fact the stages of total generation distribution and assignment have been recalculated to cater for generated traffic.As a result, a marked improvement in the relation between supply and demand has emerged. Moreover, a slowdown in urban sprawl and an increase in the density of activities in smaller and greater suburban areas have been noted. The economic benefits of such an undertaking would approach 73,000 h saved per evening rush hour.The automatic highway network would lengthen commuting distances by 3.5% while reducing commuting time by 2.6%. Thanks to the highway alone covering 2% of the entire infrastructure it would comprise 4.3% of total commuting distance in only 1% of commuting time. It would moreover increase the average commuting speed by 6.3%.     

铁路快捷货运网络布局研究

构建铁路快捷货运网络,提高铁路市场竞争力,对提高铁路运输经济效益和社会效益具有重要意义.综合考虑城市规模、快捷货物运输需求、对外通道连接情况等多种影响因素,提出构建由铁路快捷货运枢纽中心、快捷货运集散中心和快捷货运集散点组成的分层次城市节点网络;结合铁路网中长期规划和建设情况,探讨构建覆盖快捷货运城市节点的分层次铁路快捷货运通道网络布局方案.     

铁路运输网络特征的分析与探讨

网络产业的生产可以分为基础设施和生产运营两个层面。基础设施的网络特征决定了网络的连通性和网络上的运输量对运输经营的收益和回报有直接影响。铁路运输应通过增加基础设施的数量和运输量、加强基础设施的互联互通、改善运网关系,以获得较大发展。     

Freight transportation demand elasticities: a geographic multimodal transportation network analysis

This paper presents direct and cross-elasticity estimates of the demands for three freight transportation modes: rail, road and inland waterways. They are computed for 10 different categories of goods with a detailed multimodal network model of Belgian freight transports. The model, which minimises the generalised cost of transportation tasks defined by O-D matrices, assigns traffic flows to the different modes, transport means and routes. Successive simulations with different relative costs permit the computation of specific arc-elasticities. In contrast with the usual methodologies, the present methodology is not based on a statistical analysis of disaggregate data on actual modal choices and transport tariffs. This is a particularly useful feature since such data are mostly not available for freight transports in Europe. Furthermore, it fully takes into account the detailed characteristics of the network, all available routes and combinations of modes, as well as the specific localisation of activities within the network. Its estimates are compared with previously published estimates, and, in particular, with Abdelwahab's results published (1998) in this journal.     

Decomposing the decoupling of Danish road freight traffic growth and economic growth

In recent years many European countries have seen a decoupling of the growth in road freight traffic (vehicle kilometres) from economic growth. A similar decoupling has not been observed in road freight transport (tonne kilometres). In this paper the historical growth in national Danish road freight traffic and transport is attributed to causes using a Divisia index decomposition method. It is demonstrated that overall road freight traffic growth is a consequence of often opposite pointing growth effects in the underlying factors. The observed decoupling of road freight traffic growth from economic growth is mainly the result of use of larger vehicles, increasing average loads, and less empty running. Growth in road freight transport is primarily caused by growth in production. A decrease in the number of tons lifted per tonne produced (the handling factor) is offset by an increase in the tonne kilometres per tonne lifted.     

A freight transport optimization model for integrated network,service, and policy design

This paper presents a freight transport optimization model that simultaneously incorporates multimodal infrastructure, hub-based service network structures, and the various design objectives of multiple actors. The model has been calibrated and validated using real-life data from the case study of hinterland container transport of the Netherlands, where CO₂ pricing, terminal network configuration, and hub-service networks are chosen as the design measures. Policy packages combining multiple types of policies show better network performance as compared with the optimal performance resulting from a single policy type. This illustrates the value of incorporating multiple types of policies simultaneously in freight transport optimization.     

Sustainable efficiency drivers in Eurasian airports: Fuzzy NDEA approach based on Shannon's entropy

This research explores the physical infrastructure and flight consolidation efficiency drivers of Eurasian airports regarding their infrastructure and movement productivity levels. A novel Fuzzy Double-Frontier Network DEA (FDFNDEA) model is proposed to investigate the relationship between desirable (freight and passenger turnovers) and undesirable (pollutant emission levels due to aircraft movements) outputs against the respective infrastructure usage, fuel consumed, and movements performed at each of the 23 Eurasian airports from 2000 to 2018. This balance between desirable and undesirable outputs emerges spatially and temporally due to the evolution of the airport system's productive resources at each one of the Eurasian countries over the period observed. Shannon's entropy is used as the cornerstone to quantify the input and output vagueness of this evolution in Triangular Fuzzy Numbers (TFN), thus allowing the accurate building of alternative optimistic and pessimistic double-frontier efficiency. Differently from previous research, Shannon's entropy is the key for measuring input and output vagueness levels in light of the maximal entropy principle. This principle states that the distribution that best represents the current state of knowledge is the one with largest entropy. Maximal entropy yields bias-free decision-making in the sense that the input/output distributional profiles for Eurasian airports contain the maximal possible heterogeneity, working as a robust or best/worst-case scenario against eventual unconsidered assumptions. Hence, optimistic and pessimistic Malmquist Productivity Indexes (MPI) for overall and each stage productivity results are subsequently regressed against contextual variables related to airport characteristics and regional socio-demographic and economic indicators of each Eurasian country using bootstrapped Cauchy regressions. The findings revealed the spatial heterogeneity of productivity factors and airport performance across Eurasia. Results also demonstrated the negative impact of income inequality and the positive impact of private participation on technological progression in the Eurasian airport industry.