Insights into carsharing demand dynamics: Outputs of an agent-based model application to Lisbon,Portugal

Two important claims for carsharing systems are their increased flexibility and potential contribution to reducing transport externalities such as pollution. Carsharing typically involves a fleet of vehicles in stations around a city that clients may use on an hourly-payment basis. Classical round-trip systems address a niche market of shopping and errand trips. However, a growing market is now arising providing one-way trips to clients. Great uncertainty remains on the economic viability of this type of carsharing given the complex relation between supply and demand, and how this may influence the level of service provided. Realistic modeling tools that include both supply and demand characterization and allow testing several carsharing operational parameters are scarce. In this sense, a detailed agent-based model was developed to simulate one-way carsharing systems. The simulation incorporates a stochastic demand model discretized in time and space and a detailed environment characterization with realistic travel times. The operation includes maintenance operations, relocations and reservations. The model was applied to the case-study city of Lisbon. Our results show that comparing to other modes, carsharing performs worse than private cars both in terms of time and cost. Nevertheless, it clearly outperforms taxis in terms of cost, and outperforms buses, metro and walking in terms of travel time. The competitiveness of carsharing is highly determined by trip length, becoming more competitive than other modes (travel-time wise) as trips become longer. The operational policies as car-fleet relocation and car reservation showed significant effects in enhancing profit while preserving good customers' satisfaction.     

The impact of flight delays on passenger demand and societal welfare

US airline passengers increasingly have access to flight delay information from online sources. As a result, air passenger travel decisions can be expected to be influenced by delay information. In addition, delays affect airline operations, resulting in increased block times on routes and, in general, higher carrier costs and airfares. This paper examines the impact of flight delays on both passenger demand and airfares. Delays are calculated against scheduled block times as well as against more idealized feasible flight times. Based on econometric estimations, welfare impacts of flight delays are calculated. We find that flight delays on a route reduce passenger demand and raise airfares, producing significant decreases in both consumer and producer welfare. Since producer welfare effects are estimated to be three times as large as consumer welfare effects, we conclude that from an economic efficiency rationale, airlines should be required to pay for the bulk of flight delay remediation efforts.     

A method for the design of optimal transport strategies

This paper presents a methodology for the design of optimal transport strategies and demonstrates its application to six UK cities. An objective function representing the total welfare of a transport strategy is used to measure the performance of the strategy; the levels of policy instruments in a strategy, such as changes in public transport fares and frequency, are chosen such that the objective function is optimised. Two types of analysis are reported: sensitivity tests around individual policies to examine their relative impacts, and optimisations of packages of transport policies. The effects of spatial variations of the PT policies in the optimisations are also investigated.     

A game theory approach to urban public transport integration policy

A game theoretic conceptual framework model is presented to highlight strategies undertaken by individual public transport operators, public or private, vis-à-vis operational integration strategies. The Nash equilibrium is used to identify possible outcomes in various market situations. These are compared with reported case studies. The model, as a strategy-guiding tool, may be used to assist transport policy decision-makers concerned with public transport integration in identifying the most cost-effective form of intervention and its timely implementation.     

A dynamic demand analysis of the United States air-passenger service

This study examines the short- and long-run effects of various determinants on the demand for US air passenger-services using the Johansen cointegration analysis and a vector error-correction (VEC) model. Results show that, in the long-run, airfare, disposable income and NASDAQ have significant effects on US air travel demand. The combined short-run dynamic effects of disposable income, NASDAQ, population and airfare jointly explain changes in air passenger-miles. Finally, we find that the 9/11 terrorist attacks drop air passenger demand by 5% during 2001:Q3-2002:Q2, which in turn pushes down the seat capacity by 4%. However, it has little impact on airfare.     

Assessing airport terminal performance using a system dynamics model

Current models for airport terminal performance assessment require substantial modeling effort to be customized to the configuration of a particular airport terminal and to reflect adequately the alternative airport operational policies adopted in a user-friendly way. Therefore, there is a need to develop a generic, yet flexible decision-support tool that will facilitate high-level decision-making related to fundamental changes in the structure and operation of the airport terminal system. This paper presents a generic and easily customizable system dynamics based tool for assessing the performance of the Athens International Airport passenger terminal under different demand and resource deployment scenaria.     

A random utility maximization (RUM) based measure of accessibility to transit: Accurate capturing of the first-mile issue in urban transit

The paper presents a random utility-based measure of accessibility to explain the first-mile issue in urban transit. A discrete access stop/station location choice model is used to calculate the expected maximum utility of transit access choices as the measure of the proposed access to transit measurement approach. It captures the effects of changes in various personal, sociodemographic, transportation and land-use variables on access to urban transit that are overlooked by conventional approaches of accessibility measurements (count-based cumulative opportunities measures and gravity-based measures). The proposed accessibility to transit measurement approach is empirically measured for the Greater Toronto Area and is integrated into an operational tool programmed in a GIS-based traffic assignment software, TransCAD 7.0. This allows comparing it to the conventional measures, and the results reveal that the conventional measures tend to over-estimate access to transit.     

Air transport demand and economic development in sub-Saharan Africa: Direction of causality

Air transport may be a key tool to advance economic development. However, it is uncertain whether air transport boosts economic development, or vice versa. Both views have theoretical and empirical support. In some countries and regions, air transport is important for initiating development, for example by attracting foreign direct investment or granting access to lifelines. Elsewhere, economic development drives air transport demand. Establishing the direction of causality for regions/countries segmented by income level may inform pragmatic policy. This study analyzes the causal relationship between air transport demand and economic development for six sub-Saharan African countries for the period 1981–2018. Vector error correction and vector autoregression models are employed to identify long- and short-run causalities. The results reveal heterogeneous, context-specific causal relationships. In the long-run, for South Africa, Nigeria and Kenya, the direction of causality runs from economic development to air transport demand; for Ethiopia, causality runs in the opposite direction, with increased demand for air transport promoting economic development; and for Senegal and Angola, the relationship is too weak to infer causal directions. Possible explanations for this heterogeneity include differences in per capita income, low-cost carriers' share of national aviation markets, the presence of large home-based airlines, and comparative geographical advantage as a natural hub.     

Consolidation effects: Whether and how inventories should be pooled

This paper presents a framework for deciding whether and how inventories should be pooled, using the consolidation effect as a cornerstone tool to measure inventory costs, service levels, and total costs. Based on the random generation of different scenarios, it is indicated the adequacy of inventory centralization, regular transshipments, and independent systems to a given set of demand, lead time, and holding costs characteristics. Sensitivity analyses on mathematical expressions are performed to determine when one alternative is preferable in terms of total costs. Real settings are also presented in light of the framework developed.     

Bi-level optimization approach for configuring population and employment distributions with minimized vehicle travel demand

Compact development aims to lead to dense and mixed distributions of population and employment in land use planning which may result in reduced vehicle miles traveled (VMT). However, determining an optimum or desirable configuration of population and employment distribution to achieve the compact development goal remains challenging due to numerous competitive development alternatives or possible exacerbated traffic congestion as a result of over-intensification of urban land use. To address this challenge, a systematic approach is proposed with a bi-level optimization model aiming to find out an efficient population and employment map for vehicle travel reduction. The upper level of the model is formulated to minimize VMT and vehicle hours traveled (VHT) varying with possible changes in population and employment densities. The lower level is based on a tour-based travel demand model to mechanistically represent the response of travel choices to those changes. The programming is solved by a Genetic Algorithm. The proposed method is demonstrated through a case study of Hamilton County, Ohio, U.S. The results indicate that a more compact urban form reduces VMT; however, it may cause longer VHT depending upon the density. To avoid urban overconcentration and reduce both VMT and VHT simultaneously, a compact urban development configuration with a population density < 5289 persons/mi² and the employment density < 3282 jobs/mi² is recommended for the area. As a negative relationship demonstrated between transit headway reduction and vehicle travel demand, strategies for improving transit provision are helpful to reducing vehicle travels in compact development scenarios.     

Measuring the effect of transportation infrastructure on retail firm co-location patterns

This paper studies the effects of transportation infrastructure on the location behavior of competing retail firms. First, in a game theoretic framework that describes the location choices made by retailers with respect to each other, the connection between relative firm location and transportation demand is outlined. Second, a multivariate point pattern statistic based on this theoretical framework is applied to location patterns of fast food outlets to measure the effects that major road infrastructure has on firm location behavior in this sector.The results suggest that transportation infrastructure affects the location behavior of firms with respect to their location in relation to their competitors. Access to important transportation infrastructure induces competing outlets to locate next to each other—a tendency not necessarily observed among outlets without such access. Theoretically, this does not only affect economic outcomes, but also travel demand and consumer accessibility. The findings from this study stress the importance of accounting for how transportation infrastructure changes the location behavior of firms in travel demand frameworks.     

Business connectivity,air transport and the urban hierarchy: A case study in East Asia

This paper explores the effect of business connectivity between cities on their air traffic connections, and in turn on their place in a region's urban hierarchy. Its focus of attention is East Asia, where economic development is underpinned by a complex set of international flows of trade and investment. Business connectivity is a key part of these flows. The research incorporates a measure of business connections in a regression model that previously relied on GDP per head, population and distance to account for international air links. Results confirm that business connectivity is a more important influence on the level of international air links within East Asia, and plays a major role in explaining the changes in city rank over time. The paper concludes with suggestions that possible incorporation of domestic air travel (itself larger than the intra-regional flows in this region) could enrich the insight of this approach.     

Relative logistics sprawl: Measuring changes in the relative distribution from warehouses to logistics businesses and the general population

The logistics sprawl – warehousing and distribution centers relocating farther away from central urban areas to the urban periphery – has been widely examined in multiple global trade gateways. The spatial shifts have been attributed to the systematic and geographic restructuring of goods production and distribution systems at the global scale. More recently, growing online shopping sales and demand for instant delivery have put tremendous pressure on online retail businesses to locate order fulfillment centers in urban areas with direct access to the consumer markets. Has the trend of sprawling warehouses reversed? Have warehouses been relocating closer to consumer demand? In this research, I use a relative distribution measure to quantify the spatial distribution of warehouses relative to the logistics sector, the goods movement sector, and the general population over time. The main data source is ZIP Code Business Patterns from 2003 to 2016 with the study area of the 64 largest US metropolitan areas. In 2016, warehouses were most closely distributed relative to logistics sectors (38.6 km), followed by goods movement sectors (41.2 km), and population (43.5 km). From 2003 to 2016, the distance between warehouses and related businesses has increased, but the extent varies with respect to metropolitan and warehouse size. The trend of increasing relative distance from warehouses to related businesses stopped since the economic recession in 2008. Relative distribution measures are significantly correlated with internal ground shipment ton-kilometers but only in large trade gateways.     

Distortional Bullwhip Effects on carriers

This paper analyzes the Bullwhip Effect (BWE) problem from the (carriers’) viewpoint. The analysis explores how retailer’s limited capability to forecast end-customer demand and their sub-optimal replenishment policies distort service demand signals to carriers. The consequent unnecessary increases in carriers’ capacity costs and operational instability are quantified for a context of pronounced seasonality. The paper finds that carriers unable to adjust transportation capacity to seasonal changes can incur costs of nearly five times what is possible with maximum forecasting capabilities and prudent replenishment policies. Another major finding is that replenishment policy is superior to forecasting capability in reducing BWE-related costs.     

考虑换乘费用的城市公共交通票价优化

换乘所产生的附加费用,如时间和票价等,导致配流影响因素产生变化,如果沿用传统方式将降低预测精度和可靠性。通过引入换乘次数和方式等因子计算出行等待、乘车、换乘及风险评估预留时间等,定义广义出行费用与计算方法;建立双层规划模型求解最优票价,最后通过算例分析弹性出行需求、换乘费用、票价之间的关系。计算结果表明,换乘费用对出行需求的影响小于票价优化对出行需求的影响,优化票价随换乘费用增加而加速降低,为公共交通票价优化提供研究依据。     

Estimating welfare changes from efficient pricing in public bus transit in India

Three different and feasible pricing strategies for public bus transport in India are developed in a partial equilibrium framework with the objective of improving economic efficiency and ensuring revenue adequacy, namely average cost pricing, marginal cost pricing, and two-part tariffs. These are assessed not only in terms of gains in economic efficiency, but also in changes in travel demand and consumer surplus. The estimated partial equilibrium price is higher in all three pricing regimes when compared to the current price. As a result, consumer surplus falls in all three cases. The price increase is much larger with average cost pricing compared to marginal cost pricing or two-part tariffs, and hence a larger fall in demand and consumer surplus occurs due to average cost pricing. While there is a gain in economic efficiency from marginal cost pricing and two-part tariffs, this improvement comes at the expense of reduced public bus transit demand and consumer surplus, given the price inelastic public bus transit demand estimated for India. Given the mobility needs and the developmental concerns of a growing economy such as India, the challenge for policy makers is to balance the gains in economic efficiency in the public bus transit sector against other social, political, and developmental goals.     

Economic geography and transportation conditions with endogenous time distribution amongst work, travel, and leisure

This study examines possible effects of transportation conditions upon economic growth and geography. The paper proposes a model of economic growth with travel time and cost, housing, residential distribution, amenity, and endogenous time distribution amongst work, travel, and leisure. It deals with a dynamic interaction among capital accumulation, land use, housing market, environmental change, and transportation conditions in a linear economy. Although transportation systems are simple in this paper in the light of contemporary literature in transportation research, the paper demonstrates a way to integrating some important models in the literature in transportation research, economic growth theory and urban economics so that the significance of transportation systems upon economies can be properly analyzed.     

Mapping the potential consequences of car-use reduction in urban areas

Policy measures managing the demand for private car use are contemplated in urban areas all over the world. A first step in evaluating the effectiveness––as well as the interrelated sociospatial consequences––of travel demand management (TDM) measures is determining how their implementation changes the travel options faced by households in different segments. Geocoded travel diary data from Gothenburg, Sweden, are analysed with the aim of determining the number and type of trips by car to the city centre that would be affected by the introduction of traffic regulations varying spatially and temporally. Logistic regression analyses are performed to identify effects on different trip purposes, as well as individual and household characteristics related to changes in travel options. The possible application of the results within a policy context and to other urban areas is discussed along with the potential implications for research into adaptation strategies adopted in response to the implementation of TDM measures.     

The relationship between airport performance and privatisation policy: A nonparametric metafrontier approach

The assessment of economic and technical efficiency is a useful tool for selecting the most appropriate technology for airport operations. However, traditional models require that the units being assessed operate with the same technology. To overcome this limitation, one can use a non-concave metafrontier approach that is based on Data Envelopment Analysis (DEA) to calculate the techno-economic efficiency and Technological Gap Ratios (TGRs) with non-homogeneous technologies for airports across countries and with different ownerships. The previous studies mainly applied DEA to measure the operational efficiency of airports. Our results indicate that privately owned airports have better technical efficiency than public ones. In addition, our empirical analysis shows that public airports in the Asia-Pacific area have the lowest techno-economic efficiency.     

Social Capital,Tourism and Regional Development: SPCC as a Basis for Innovation and Sustainability

Traditional views of regional development have focused on economic factors and potential innovation in technical and resource exploitation processes. Similarly, regional tourism development is usually couched in economic terms, such as number of jobs and increasing land values. This approach usually ignores the social and community aspects of tourism development; thus an alternative view argues that the community needs to be factored into our planning and development strategies to balance the traditional economic view. It is argued in this paper that fostering innovation in regional development is much more than a process of community consultation. Rather, what needs to be factored in is SPCC – social, political and cultural capital. This works in both directions; tourism development depends on a level of social, political and cultural capital in order to be a successful regional development tool (even in economic terms) while at the same time tourism development can be undertaken in a way that contributes to SPCC in the region. The paper outlines the key concepts of social capital, political capital and cultural capital. It does so within the context of regional tourism development and the concepts of systems of innovation and sustainable development.