New centrality and causality metrics assessing air traffic network interactions

In ATM systems, the massive number of interacting entities makes it difficult to identify critical elements and paths of disturbance propagation, as well as to predict the system-wide effects that innovations might have. To this end, suitable metrics are required to assess the role of the interconnections between the elements and complex network science provides several network metrics to evaluate the network functioning. Here we focus on centrality and causality metrics measuring, respectively, the importance of a node and the propagation of disturbances along links. By investigating a dataset of US flights, we show that existing centrality and causality metrics are not suited to characterise the effect of delays in the system. We then propose generalisations of such metrics that we prove suited to ATM applications. Specifically, the new centrality is able to account for the temporal and multi-layer structure of ATM network, while the new causality metric focuses on the propagation of extreme events along the system.     

Competition,market concentration,and relative efficiency of major container ports in Southeast Asia

This study aims at investigating the degree of market concentration of container ports in Southeast Asia and to associate the concentration tendency with efficient container operations. While Singapore is the busiest container port in the region, its premier position is threatened by the emergence of other container ports in neighbouring countries. Major top ten container ports in Southeast Asia are included in the analysis, and market concentration is evaluated using established measures and analytical techniques such as the Hirschman-Herfindahl Index (HHI), Gini coefficient, and shift-share analysis from 2007 to 2017. A super-efficiency model is then applied to the ports to investigate the association between shift effects and port efficiency. The HHI index indicates that the container port system in Southeast Asia has become ‘moderately concentrated’ with a score of 0.21 in 2017, contrasting with an index of 0.27 in 2007 suggesting it was ‘highly concentrated’ indicating a tendency towards de-concentration. ‘Super efficiency DEA’ results suggest that Laem Chabang and Singapore ports are ‘efficient’ exhibiting efficiency scores higher than one, while the other eight ports are ‘less efficient’. It is also found from the association of the net-shift effects and efficiency scores that Laem Chabang is the only port that is efficient and gaining market share, and, more importantly, and perhaps surprisingly, the ports gaining market share are ‘inefficient’. This study contributes to the literature not only by investigating the concentration tendency of the fast growing container port system of Southeast Asia, but also by associating efficiency evaluations with the market concentration.     

Characterizing the Brazilian airspace structure and air traffic performance via trajectory data analytics

This paper presents a data-driven approach for multi-scale characterization of the Brazilian airspace structure and air traffic operational performance from aircraft tracking data recorded by surveillance systems. Unsupervised learning is performed with a flight trajectory clustering analysis to automatically identify spatial traffic patterns in both the terminal and the en route airspace for major origin-destination pairs of the Brazilian air transportation system. Based on the as-flown route structure learned, quantitative metrics are developed to describe the structural efficiency of the airspace and the operational efficiency of the traffic flows. For this, actual flight trajectories are projected onto reference nominal trajectories in space and time. The results allowed for cross-route comparisons of air traffic flow efficiency across multiple flight phases as well as for the identification of causal factors for trajectory deviations from nominal routes. An interactive data analytics tool is also created to output performance statistics and air traffic visualizations. With the provision of a systematic data-driven approach for characterizing actual air traffic operations, the analytics framework is envisioned to assist airspace design and performance monitoring processes and to provide the basis for developing predictive capabilities in support of traffic flow management.     

The impact on traffic,market shares and concentration of airline alliances on selected European—US routes

This paper examines the impact of airline alliances on traffic of the constituent airlines using an analysis of US Bureau of Transportation Statistics T-100 International Market Data on a monthly basis for five routes to the US from European hubs. The European hubs are Frankfurt and Paris. The period covered is January 1990–December 2003; a sufficiently lengthy period to enable the derivation of good time-series models before the ‘intervention’ of alliance formation and development. The alliances focussed on are Air France and Delta, part of the SkyTeam Alliance and Lufthansa and United Airlines, part of the Star Alliance. It is possible to distinguish code sharing agreements and then the subsequent immunity from US antitrust legislation. It is also possible to suggest some conclusions on the differences in alliance development in the more liberal open skies environments adopted by many European countries with the more traditional, stricter regulated bilaterals that exist in others such as the UK. Competition is examined using the Hirschman-Herfindahl Index so as to throw light on the impact of alliances on market concentration by route.     

International air network structures and air traffic density of world cities

This paper examines international air passenger and cargo flows within and among Asia, Europe, and America, and the degree of air traffic density for major cities worldwide, using a basic gravity model composed of GDP, population, distance, and several dummy variables. The results reveal that many cities are strengthening their position as international air transportation hubs, especially: Tokyo, Hong Kong, Singapore, London, Paris, Frankfurt, Amsterdam, New York, and Miami. Finally, the results show that the air traffic density of three cities, Seoul, Hong Kong, and Amsterdam, is growing at an extraordinary rate.     

Comparing the impacts of local land use and urban spatial structure on household VMT and GHG emissions

To highlight the role of sustainable urban spatial structure in reducing household vehicle miles traveled (VMT) and CO₂ emissions, this empirical study of the 121 largest urban areas (UAs) in the U.S. compares the effects of local land use and UA scale spatial structure in a multilevel analysis framework. The results show that centralized population and mezzo scale jobs-housing balance as well as higher UA population density can significantly reduce VMT and CO₂ emissions. The combined effects of all UA level variables, including population-weighted density (PWD), are found to be on par with the elasticity of VMT with regard to a census tract level compactness index. Further, we find that urban spatial structure moderates local urban form effects on travel behavior. For example, while 10% more compact census tracts are associated with 5% fewer VMT in UAs with the sample average PWD, such as St. Louis and Pittsburgh, this estimated local effect increases to 7.5% and 10% in UAs where PWD is as high as in Chicago and New York, respectively. The findings of this study strongly support policy programs that aim to boost “articulated densities” in the urban region and call for stronger institutional frameworks for regional planning.     

Impact of high-speed rail on market concentration and Lerner index in China's airline market

China has become the second largest air transport market in the world since 2005. Its total length of high-speed rail (HSR) tracks in operation has been greater than that of all other countries combined since 2012. HSR poses a significant challenge to the Chinese airline industry, especially on major airline routes. The impacts of HSR on two market-competition measures, namely, the Herfindahl–Hirschman Index (HHI) and the Lerner index, are examined in this study. In general, the entry of HSR had the effect of reducing market power measured by both the unweighted and weighted Lerner indexes. However, the Lerner index and HHI of the routes with parallel HSR services remained consistently higher than those of the routes without parallel HSR services.     

Characterization of delay propagation in the air traffic network

We build a delay propagation network based on Bayesian Network approach to study the complex phenomenon of delay propagation within a large network consisting of the 100 busiest airports in the United States. Through topological analysis and probability analysis, we investigate the characterization of delay propagation among airports and the impact of different types of airports on delay propagation. Results indicate that the cumulative degree distribution of the delay propagation network follows an exponential function and flight delays take at most one transhipment to go from each airport to any other airports on average. For each individual airport, the effects of delay propagation are associated with airports size (traffic flow), small airports are easily affected by other airports while large airports are more affecting downstream airports but fewer affected by upstream airports. Finally, we show how the number of affected airports changes as a function of the delayed airports based on different simulation strategies.     

Optimizing and assigning price levels for air traffic management

Pricing policies could encourage airline companies to modify departure times and routes of their flights in order to reach a route-slot allocation target that minimizes the en-route congestion. The problem of restricting the number of price levels and the assignment of one price level to each sector at each time period is studied using a simulation based on a Logit discrete choice model. In this model, an option is defined as the combination of a departure time and a route. For each flight, a utility is associated to each option and takes into account the flying cost, the cost of ground delay and the prices of crossed sectors. The optimization of the pricing policy considers average flows and minimizes the quadratic difference between desired and expected flows on each option. A heuristic algorithm that involves successive iterations of simulated annealing and gradient methods performs this optimization. The simulated annealing assigns a price level to each sector at each time period, and the gradient algorithm computes new values of price levels. The test of the method on constructed examples indicates that the use of only four price levels does not significantly deteriorate the performance of the system with respect to the use of independent prices.     

Challenges to domestic air freight in Australia: Evaluating air traffic markets with gravity modelling

With two of the busiest air traffic corridors globally, Sydney-Melbourne (SYD-MEL) and Sydney-Brisbane (SYD-BNE), very liberal open skies agreements, and the world's most isolated large city in Perth, air freight in Australia should be destined for substantial growth, but has in contrast to other regions such as the US not yet materialised. This paper identifies challenges surrounding domestic air freight markets in Australia and compares the provision of road vs air freight services utilising gravity modelling methods. Our findings suggest the impedance of domestic air freight services in Australia is greater for regional areas between the primary cities (such as Canberra, between Sydney and Melbourne) than remoter areas (such as Cairns in Northern Australia). Our models show further that in addition to distance, air freight capacity on any of our analysed routes is despite being demand-pulled in terms of GDP dependency significantly attuned to factors at both the origin (in particular domestic trade capability, i.e. manufacturing and logistics) and destination.     

Why standard modelling and evaluation procedures are inadequate for assessing traffic congestion measures

As traffic congestion in Hong Kong worsens with the growing use of motor vehicles, to determine what has to be done to achieve and maintain an acceptable level of mobility for persons and goods becomes the subject of intense debate by economists, planners and politicians. Although many traffic congestion measures have been suggested and investigated, they are mainly confined to expansion of transport infrastructure and measures to make effective use of roads. New roads and public transport improvements may encourage increases in traffic and changes in the patterns of trips, while traffic management and regulation measures may in turn lead to suppression in road traffic. In order to evaluate these measures, it is required to make use of a transport model in assessing their traffic impacts. However, there are always discrepancies between the traffic forecasts and the actual flows on the roads. This paper investigates why the standard modelling and evaluation procedures currently used by the Hong Kong Government are inadequate for assessing the traffic congestion measures. Empirical evidence is given together with discussion on modelling and evaluation issues raised by the existence of suppressed/induced traffic.     

Hub airport slot Re-allocation and subsidy policy to speed up air traffic recovery amid COVID-19 pandemic --- case on the Chinese airline market

With international air travels largely banned around the world amid the global COVID-19 pandemic, many gateway and hub airports have more ideal slots available for reallocation. Airport traffic recovery replaces airport congestion to become the primary challenge of major airports around the world. With the pandemic well controlled domestically in China, the government liberalizes the hub airport slots for those previously forbidden services to the small/regional airports. This paper thus analytically examines the effect of this slot liberalization. The government subsidy to the small airports has also been considered. It is found that the slot liberalization can speed up airport traffic recovery for both hub and small airports. The hub airport slot liberalization leads to a lower level of minimum subsidy to sustain the survival of the small airports. Given any fixed level of subsidy to the small airport, both the total airport traffic and social welfare would improve with the slot liberalization at the hub airport. When the government can adjust the level of subsidy after liberalizing the hub airport slots, the subsidy could be excessive, if the government emphasizes too much on airport traffic recovery. This would, however, harm the overall social welfare.     

Spatial concentration and connectivity of international passenger traffic at Brazilian airports

This paper examines concentration and connectivity of international passenger airport traffic in Brazil. The analysis considers seat supply and scheduled flights from 1999 to 2012. The 2000–2005 period was marked by concentration and limited international flight links, which was followed by the movement to recover capacity and connectivity from 2005 to 2010. Brazil started to liberalize bilateral agreements in 2002, and eventually moved towards the “open skies” concept in 2010, facilitating the process of operational de-concentration and increasing seat supply. The Brazilian government's liberalisation policy through bilateral agreements did not spark off a significant turnaround for national airlines; rather, the revived traffic growth was led by foreign airlines. This movement brought significant changes in the composition of international passenger traffic in Brazil, although changing little in terms of concentration and connectivity. The real change was the dominance of foreign airlines and seat distribution by regions, with the Latin America and Caribbean region shrinking to less than half of the market.     

An airline's management strategies in a competitive air transport market

Over the last decade, the demand for domestic and international flights in Korea has increased substantially. To meet the strong flight demands, several low cost carriers have begun to offer flight services. In addition, full service carriers have been motivated to establish their own subsidiary low cost carriers to maintain their market share against rival low cost carriers. This paper studies the management strategies of three kinds of airlines - full service carrier, its subsidiary low cost carrier and rival low cost carrier - based on game theory in the competitive air transport market. Each airline is assumed to act as a player and chooses strategies regarding airfare, flight frequency, and the number of operating aircrafts for specific routes while maximizing its own profits. Demand leakages between the airlines are considered in the flight demand function according to the selected strategies of all airlines. Through various game situations reflecting realistic features, this study provides managerial insights that can be applied in the competitive air transport market.     

A spatial analysis of air transport access and the essential air service program in the United States

In the United States, the goal of essential air service (EAS) is to provide a minimum level of air transport service from smaller, often remote communities to the national network. While supporters of EAS tout the economic benefits of connecting rural and isolated communities, critics cite high costs, low use and antiquated eligibility requirements as factors which compromise the value of the program. In this paper, a comprehensive database of US airports is combined with network analysis techniques and a geographic information system to evaluate population access (at the census tract level) to EAS airports for 2006. Results suggest that redundant coverage of EAS market areas by alternative Federal Aviation Administration designated hub airports can contribute to EAS airport market leakage and that alternative definitions of EAS community eligibility have the potential to dramatically increase programmatic efficiency and reduce federal monies spent on EAS subsidies.     

Statistical characterization of deviations from planned flight trajectories in air traffic management

Understanding the relation between planned and realized flight trajectories and the determinants of flight deviations is of great importance in air traffic management. In this paper we perform an in-depth investigation of the statistical properties of planned and realized air traffic on the German airspace during a 28 day periods, corresponding to an AIRAC cycle. We find that realized trajectories are on average shorter than planned ones and this effect is stronger during night-time than day-time. Flights are more frequently deviated close to the departure airport and at a relatively large angle-to-destination. Moreover, the probability of a deviation is higher in low traffic phases. All these evidences indicate that deviations are mostly used by controllers to give directs to flights when traffic conditions allow it. Finally we introduce a new metric, termed di-fork, which is able to characterize navigation points according to the likelihood that a deviation occurs there. Di-fork allows to identify in a statistically rigorous way navigation point pairs where deviations are more (less) frequent than expected under a null hypothesis of randomness that takes into account the heterogeneity of the navigation points. Such pairs can therefore be seen as sources of flexibility (stability) of controllers traffic management while conjugating safety and efficiency.     

Transit-based job accessibility and urban spatial structure

Job accessibility is a measure of people, opportunities, and transportation system that are fundamental elements of urban spatial structure. Therefore, job accessibility can be used as a tool to understand urban spatial structure. Studying transit-based job accessibility can provide more insight into inner cities. To study transit-based job accessibility, a person-based approach is needed in order to take full consideration of the elements. However, person-based approaches are substantially restricted by the availability of individual trip data. This paper takes a simulation approach to study transit-based job accessibility. First, transit-dependent worker agents are generated using a population synthesis. Then the agents are enabled with job search and commuting capabilities. Once the agents are deployed in a commuting simulation, individual commuting trips are recorded. An individual job accessibility index is developed based on simulated commuting trips. The index is normalized with an expected value of 1.0 and a measurable uncertainty level, which makes it easy to interpret and suitable for cross-regional studies. A case study is conducted in Tucson, Arizona, where about 10,000 transit-dependent worker agents produce more than 600,000 individual commuting trips during morning and afternoon peak hours. Census block, group-level job accessibility shows a random spatial pattern that coincides with a dispersed urban spatial structure of the case study area.     

Institutional and structure changes in air navigation service-providing organizations

Airlines markets throughout the world have gradually gone through a liberalization process over the past 25 years. Regulatory changes involving other parts of the air transportation supply chain have globally been the subject of far less dramatic changes, and indeed some elements are still largely publicly owned monopolies. There have, however, been gradual reforms to the ways in which are traffic control and navigation services are being provided. A diversity of models has gradually emerged, ranging from traditional state ownership, through a variety of corporatized structures, to regulated private companies. While many of these new institutional forms are still at a relatively early stage in their history and development, there is still scope, using fairly well-established managerial economic approaches, to assess the implications of their structures. The analysis is based on a multi-dimensional performance matrix (e.g., including safety and financial considerations) and embraces a diversity of institutional models from around the world (e.g., a public/privatize partnership in the UK, a non-share corporation in Canada and Switzerland, and state owned in France and the US).     

Effect of concentration in airline market on Spanish airport technical efficiency

This paper tries to measure the effect of airline market concentration on airport technical efficiency. With this aim, a Stochastic Frontier Analysis (SFA) is applied, estimating with a one-step procedure technical efficiency and the effect of airlines' market power on that efficiency. Results suggest that when airports are lowly concentrated increasing concentration reduces such inefficiencies. However, this effect practically disappears when airports are highly concentrated. Additionally, the government's policies to improve airports' performance seems to have a positive effect in the short run.     

Domestic air passenger traffic and economic growth in China: Evidence from heterogeneous panel models

This paper applies recent panel methodology to examine the short-run dynamics, the long-run equilibrium relationships and the Granger causal relationship between economic growth and domestic air passenger traffic. It is based on the quarterly panel data of 29 provinces in China from the period of 2006Q1 to 2012Q3. Tests for panel unit roots, cointegration in heterogeneous panels and panel causality are employed in a bi-variate panel vector error correction model (PVECM), which is estimated by the system generalized moment method (SYS-GMM). The results show evidence of a long-run equilibrium relationship between economic growth and domestic air passenger traffic. Specifically, 1% increase in the air passenger traffic is found to lead to an increase of 0.943% in real gross domestic product (GDP). A long-run and strong bi-directional Granger causal relationship is found between these two series. It is also found that there is a short-run uni-directional Granger causality running from the domestic air passenger traffic to the economic growth.