CO2 emissions associated with hubbing activities in air transport: an international comparison

Hubbing is an important operational practice in air transport. Many studies have been conducted to examine the benefits and impacts of hubbing from an economic perspective. However, its impact on CO₂ emissions, especially across different air spaces, is not well understood. This paper explores the impact of hubbing activities in air transport from an environmental perspective. With a detailed methodology and data from the Greek and Hong Kong/Sanya flight information regions (FIRs), three levels of CO₂ emissions are estimated: airport-based, airspace-based and flight-based. After contrasting the CO₂ emission efficiencies of Athens International Airport (AIA) and the Hong Kong International Airport (HKIA), aircraft type and flight distance are examined to explain their emission efficiency differences. It is found that HKIA is associated with poorer CO₂ emission efficiency at the airport and airspace levels because of the larger aircraft and longer flight distance. However, when CO₂ emission efficiency at the flight level is considered, HKIA, with a higher passenger load factor, performs better. Major international hub airports should implement additional environmental measures to minimize the impact of hubbing activities on CO₂ emissions at the airport and airspace levels.     

Network-wide assessment of ATM mechanisms using an agent-based model

This paper presents results from the SESAR ER3 Domino project. Three mechanisms are assessed at the ECAC-wide level: 4D trajectory adjustments (a combination of actively waiting for connecting passengers and dynamic cost indexing), flight prioritisation (enabling ATFM slot swapping at arrival regulations), and flight arrival coordination (where flights are sequenced in extended arrival managers based on an advanced cost-driven optimisation). Classical and new metrics, designed to capture network effects, are used to analyse the results of a micro-level agent-based model. A scenario with congestion at three hubs is used to assess the 4D trajectory adjustment and the flight prioritisation mechanisms. Two different scopes for the extended arrival manager are modelled to analyse the impact of the flight arrival coordination mechanism. Results show that the 4D trajectory adjustments mechanism succeeds in reducing costs and delays for connecting passengers. A trade-off between the interests of the airlines in reducing costs and those of non-connecting passengers emerges, although passengers benefit overall from the mechanism. Flight prioritisation is found to have no significant effects at the network level, as it is applied to a small number of flights. Advanced flight arrival coordination, as implemented, increases delays and costs in the system. The arrival manager optimises the arrival sequence of all flights within its scope but does not consider flight uncertainties, thus leading to sub-optimal actions.     

The impact of hubbing concentration on flight delays within airline networks: An empirical analysis of the US domestic market

This paper explores the relationship between hubbing activities and flight delays in the United States from an airline-specific network perspective. Airline hubbing is measured with the Hubbing Concentration Index. We estimate the impact of hubbing behavior on delays, using three measures of delay, two based on delay against schedule, and the third based on buffer-corrected excess travel times. A significant (and positive) influence of hubbing concentration can only be found for the latter delay indicator. We conclude that airlines use buffer times to mitigate passenger-perceived delays against schedule that would, without buffers, arise from more complex network operations.     

A study on travelers' transport mode choice behavior using the mixed logit model: A case study of the Seoul-Jeju route

This study is to analyze passengers' choice of the mode of transportation when air transportation is in competition with high speed rail (HSR). The Seoul-Jeju route analyzed as an empirical case study, in which the construction of an undersea tunnel to connect Seoul and Jeju city by HSR has been considered. The study also included two new variables, ‘safety of transportation’ and ‘availability of duty free shopping’ in addition to traditional transport choice variables such as travel time, travel costs and frequency of service to reflect special characteristics of the market. As data gathering tools, SP techniques and mixed logit model, for analytical methodology, were utilized. The authors found that the goodness of fit of the models was improved with new variables. The models also showed that the characteristics of business passengers and leisure passengers in choosing the mode of transportation were different. Business passengers were apt to choose a safety secured mode of transportation regardless of fare while leisure passengers preferred to use duty free shops more than business passengers.     

Proposed revisions of regulation 261/2004: Endangering passengers’ rights and going against the international trend?

This paper analyses the 2020 revisions of Regulation 261/2004 published in February from a passenger perspective. While current Regulation 261 is criticised for being too consumer-friendly, the proposal takes the opposite stand. As it now stands, the proposal endangers passengers’ rights by increasing delay and cancellation lengths or by excluding delays at non-EU airports. The inclusion of tarmac delay could result in abuses from airlines. While bringing some clarity, the exhaustive list of extraordinary circumstances also creates new questions. The proposal also includes well-overdue changes such as the inclusion of missed connecting flights and a stronger role for National Enforcement Bodies (NEBs). Overall the proposal weakens passenger rights without real justifications.     

A methodology for establishing operational standards of airport passenger terminals

This paper discusses a methodology for establishing the operational standards of service performance of airport passenger terminals using a perception–response model. The proposed approach is defined by the graphical representation of passengers’ collective attitudes towards the range of operational service at an airport passenger terminal. It adopts new concepts to establish service standards through a special survey to better interpret terminal operations and service level at each facility. It is expressed in terms of passengers’ perception of various service levels and their response to the respective service conditions. The methodology may provide practical service standards of airport terminals and prove to be a practical and convenient technique to airport planners, designers, consultants, operators, and airport managers.     

Integration of HSR and air transport: Understanding passengers’ preferences

Different solutions for the integration of high-speed rail (HSR) and air transport could be implemented, ranging from very basic integration to more sophisticated systems which include ticket and handling integration. A discrete choice experiment is conducted to better understand passengers’ preferences. We estimate a number of flexible choice models, taking into account the existence of systematic and random taste heterogeneity. We obtain a range of willingness-to-pay values for service quality attributes, finding some important results that can be used to infer policy conclusions about the real attractiveness of the Air–HSR integrated alternative. In this respect, we find that schedule coordination which reduces connecting time will be crucial.     

Symmetrical design of strategy-pairs for enplaning and deplaning an airplane

Enplaning and deplaning processes are two main activities that passengers experience in an airplane. They are also the main factors contributing to the airplane turn time. Thus, both processes need to be carefully considered when designing a new strategy. The main contribution of this paper is twofold. Firstly, we propose a symmetrical design of deplaning strategies to match three typical grouped enplaning strategies (back-to-front, windows-to-aisle and reverse pyramid), in which the groups are organized in a LIFO (Last In First Out) manner. Secondly, we present an integrated cellular automaton model to describe the dynamic characteristics of passengers in the enplaning and deplaning processes. Numerical evaluation results indicate that the proposed windows-to-aisle and reverse pyramid strategies perform better in the following aspects: (i) the total operation time decreases; (ii) the two strategies are less sensitive to the load condition, e.g., luggage distribution and cabin occupancy rate; (iii) passengers’ satisfaction is enhanced since both individual waiting time and processing time lower down; (iv) the two strategies are fairer for the passengers since the difference among the groups remarkably shrinks.     

Social distancing in airplane seat assignments

This paper addresses the airplane passengers’ seat assignment problem while practicing social distancing among passengers. We proposed a mixed integer programming model to assign passengers to seats on an airplane in a manner that will respect two types of social distancing. One type of social distancing refers to passengers being seated far enough away from each other. The metric for this type of social distancing is how many passengers are seated so close to each other as to increase the risk of infection. The other type of social distancing refers to the distance between seat assignments and the aisle. That distance influences the health risk involved in passengers and crew members walking down the aisle. Corresponding metrics for both health risks are included in the objective function. To conduct simulation experiments, we define different scenarios distinguishing between the relative level of significance of each type of social distancing. The results suggest the seating assignments that best serve the intention of the scenarios. We also reformulate the initial model to determine seat assignments that maximize the number of passengers boarding an airplane while practicing social distancing among passengers. In the last part of this study, we compare the proposed scenarios with the recommended middle-seat blocking policy presently used by some airlines to keep social distancing among passengers. The results show that the proposed scenarios can provide social distancing among seated passengers similar to the middle-seat blocking policy, while reducing the number of passengers seated close to the aisle of an airplane.     

Connectivity of the European airport network: “Self-help hubbing” and business implications

This paper investigates the connectivity of the European air transportation network. A time-dependent minimum path approach is employed to calculate the minimum travel time between each pair of airports in the network, inclusive of flight times and waiting times. The connectivity offered by each alliance's network is compared with that of the overall network. The results show that roughly two-thirds of the fastest indirect connections are not operated by the alliance system; this could be exploited to enable a new passenger strategy of “self-help hubbing”.     

Examining the spatial–temporal dynamics of bus passenger travel behaviour using smart card data and the flow-comap

Over the past two decades, smart card data have received increasing interest from transport researchers as a new source of data for travel behaviour investigation. Collected by smart card systems, smart card data surpass traditional travel survey data in providing more comprehensive spatial–temporal information about urban public transport-based (UPT) trips. However, the utility of smart card data has arguably yet to be exploited fully in terms of extracting and exploring the spatial–temporal dynamics of UPT passenger travel behaviour. To advance previous work in this area, this paper demonstrates a multi-step methodology in order to render more insightful spatial–temporal patterns of UPT passenger travel behaviour. Drawing on the Brisbane, Australia, bus network as the case study, a smart card dataset was first processed in combination with General Transit Specification Feed (GTFS) data to reconstruct travel trajectories of bus passengers at bus stop level of spatial granularity. By applying geographical information system-based (GIS) techniques, this dataset was used to create flow-comaps to visualise the aggregate flow patterns at a network level. The flow-comaps uncovered the major pathways of bus passengers and its variations over a one-day period. The differences within the flow-comaps were also quantified to produce weighted flow-comaps that highlighted the major temporal changes of passenger flow patterns along a number of stop-to-stop linkages of the bus network. The proposed methodology visually unveiled the spatial–temporal travel behaviour dynamics of UPT passengers and, in doing so, showed the potential to contribute to a new evidence base with the capacity to inform local public transport policy.     

Measuring destination-based segregation through mobility patterns: Application of transport card data

This study explores the level of segregation experienced by seniors, children/youth, and passengers with disabilities, compared to normal-fare passengers at their trip destination when using public transportation. One week's travel records of public transit passengers were extracted from Seoul's transport card data to compute dissimilarity and exposure indices, theoretically equivalent to those developed in segregation research, to capture destination-based segregation through mobility patterns. Additionally, a multigroup entropy index was computed to measure diversity by assessing the social mixture of all passenger flows in a spatial unit. The results revealed that segregation levels experienced by passengers based on their social groups are notably different depending on the time of day and the day of the week. The computed exposure measure illustrates that the potential interaction between the selected social groups and normal-fare passengers is relatively higher during peak hours on weekdays. The results also show that subway stations provide more opportunities for interaction among different social groups. These findings can contribute to a better understanding of social segregation through mobility patterns as well as the effective quantification of the public transport network performance in terms of providing an interaction opportunity for the groups.     

The relationship between on-time performance and airline market share: a new approach

We propose a new method of modeling the relationship between on-time performance and market share in the airline industry. The idea behind the method is that the passengers’ decision to remain (use same airline) or switch (use other airlines) at time t depends on whether they have experienced flight delays at time t−1 or not. More specifically, we posit that the passengers who experienced flight delays are more likely to switch airlines for the subsequent flight than those passengers who did not experience delays. To capture such effect, we develop an aggregate-level Markovian type model that estimates the transition probability matrices separately for the passengers who experienced flight delays at time t−1 and for those who did not experience delays. The model was calibrated with the US DOT data. The study results imply that, once experiencing flight delays, passengers are more likely to switch airlines. The results also imply that on-time performance affects a carrier’s market share primarily through the passengers’ experience, and not though the “advertisement” of performance.     

A robust mathematical model and heuristic algorithms for integrated aircraft routing and scheduling,with consideration of fleet assignment problem

One of the most important airline's products is to determine the aircraft routing and scheduling and fleet assignment. The key input data of this problem is the traffic forecasting and allocation that forecasts traffic on each flight leg. The complexity of this problem is to define the connecting flights when passengers should change the aircraft to reach the final destination. Moreover, as there exists various types of uncertainties during the flights, finding a solution which is able to absorb these uncertainties is invaluable. In this paper, a new robust mixed integer mathematical model for the integrated aircraft routing and scheduling, with consideration of fleet assignment problem is proposed. Then to find good solutions for large-scale problems in a rational amount of time, a heuristic algorithm based on the Simulated Annealing (SA) is introduced. In addition, some examples are randomly generated and the proposed heuristic algorithm is validated by comparing the results with the optimum solutions. The effects of robust vs non-robust solutions are examined, and finally, a hybrid algorithm is generated which results in more effective solution in comparison with SA, and Particle Swarm Optimization (PSO).     

Conceptualizing and operationalizing nodal tourism functions

This paper reviews conceptualizations of nodal functions and presents a methodology for identifying and measuring the tourism functions of specific places with reference to place competitiveness. The methodology, which combines measures of length of stay and purpose of visit, is illustrated by a survey-based comparative analysis of ferry passengers traveling between two tourist nodes in New Zealand: Wellington and Picton. The results show distinctive differences between the two places in terms of their multiple functions expressed as origins, gateways, stopovers and destinations. Opportunities for modifying functions appear to be greatest amongst international travelers.     

Demand-responsive transit circulator service network design

Commuter rail systems are being introduced into many urban areas as an alternative mode to automobiles for commuting trips. It is anticipated that the shift from the auto mode to rail mode can greatly help alleviate traffic congestion in urban road networks. However, the right-of-way of many existing commuter rail systems is usually not ideally located. Since the locations of rail systems were typically chosen long ago to serve the needs of freight customers, the majority of current commuter rail passengers have to take a non-walkable connecting trip to reach their final destinations after departing the most conveniently located rail stations. To make rail a more viable commuting option and thus more competitive to the auto mode, a bus feeder or circulator system is proposed for transporting passengers from their departing rail stations to final work destinations in a seamless transfer manner. The key research question with operating such a bus circulator system is how to optimally determine a bus route and stopping sequence for each circulating tour by using the real-time demand information. In this paper, we name this joint routing and stopping optimization problem the circulator service network design problem, the objective of which is to minimize the total tour cost incurred to bus passengers and operators with respect to minimizing the walk time of each individual bus passenger. A bi-level nonlinear mixed integer programming model is constructed and a tabu search method with different local search strategies and neighborhood evaluation methods is then developed for tackling the circulator service network design problem.     

Public transport pre-pay tickets: Understanding passenger choice for different products

Growing cashless services in the Sydney metropolitan region are motivated by the clear supply-side benefits associated with the prepayment of public transport fares. This paper examines the effect on prepay following the ‘MyZone’ fare and ticket reform in New South Wales introduced in April 2010. ‘MyZone’, introduced two new discounted and standardised prepay products, including a new, multimode ticket. Whilst these changes had implications for all public transport providers in the Sydney Metropolitan area, it had significant ramifications for the many private bus operators who, for the first time, could provide and accept tickets, which integrated their services with the state-run rail, ferry and bus network.With empirical data collected from two surveys of passengers of a private bus operator in northern Sydney this study analyses the ticket purchasing behaviour of passengers both before the fare reform, when passengers only had access to operator-specific prepay products, and post-MyZone, when the new standardised prepay products were available. The results clearly show there are significant differences in the characteristics of passengers using multi-modal versus pay-as-you-go tickets and that this difference is driven largely by age, income and whether or not the journey involved interchange. Prior to MyZone, prepay users were easily predicted and the fare and ticket reform was successful in transitioning some cash users to prepay but prepay users were no longer predictable unless separated into prepay product groups. This suggests that a policy designed to exploit the supply-side benefits associated with cashless services needs to consider that introducing only one prepay product will not address the market need of frequent users. Passengers who continued to pay cash after the fare and ticket reform showed high sensitivity to public transport cost and are those passengers with the lowest incomes. This raises policy questions of how to mitigate against the upfront costs often associated with prepay to transition less affluent, but frequent passengers, onto cashless ticketing.     

The impact of the current economic crisis on the geography of air traffic volumes: an empirical analysis

This paper presents a comprehensive analysis of air services dynamics during the recent economic crisis. Through a regression analysis, we show that at the country scale, the change in the supply of seats is highly dependent on economic growth, confirming the cyclical nature of the air sector. Hence the crisis of air services has much more affected the USA, Europe and Japan than the rest of the world. However, many countries deviate from this general trend. In a second step, using the existing literature, we explain some of these deviating figures. National specificities and airline strategies seem to influence the intensity of the crisis. We argue that the intensity of the crisis in the US is due to the structural oversupply of the air sector. Through other cases, especially the Middle East, we show that hubbing strategies might reduce the impact of the crisis, or at least make it less dependent upon local economic dynamics. In contrast with other authors, we found no positive impact of the share of low-cost carriers on the supply during the crisis, despite their success in some specific contexts like between Europe and Morocco.     

Passenger waiting time in an airport and expenditure carried out in the commercial area

A methodology to estimate the relationship between the expenditure in the commercial area of an airport and the passenger waiting time to board is developed. It shows that the more time spent in the airport, the greater consumption by passengers. This functional dependence is analysed for the travellers who travel for holiday purposes and of those who do so for business. As an example of application of this methodology the results shown are obtained from Asturias Airport (Spain).     

Airline strategies for aircraft size and airline frequency with changing demand and competition: A simultaneous-equations approach for traffic on the north Atlantic

Airport planners need to know the forecast demand on the facilities provided airside at airports. For this they need to know how airlines will deal with traffic in terms of the size of aircraft and frequency of service. In response to increasing demand, airlines may increase capacity by increasing the frequency of flights or they may choose to increase aircraft size. This may yield operating cost economies. If the airports they operate from are capacity constrained they will be limited in the extent that they can change frequency that will limit their ability to compete with the number of frequencies offered. Consequently, these airports are excluded as are major hubs as frequencies will be influenced by connecting passengers. Routes are identified on the north Atlantic that can be analysed and conclusions are suggested on the basis of three stage least-squares estimates for pooled time series-cross section data. An increase in passengers on the whole will result in a larger increase in frequency than in aircraft size but the impact of competition does not yield significant results due to the strategy of excluding certain categories of airport.