Airport Capacity Consequences Leveraging Aviation Integrated Modelling (ACCLAIM)

Lead Research Organisation: Imperial College London
Department Name: Civil & Environmental Engineering


Global air transport grows at around 5% per year, a rate that generally exceeds increases in airport capacity. This is especially true in the industrialized world, where the economic benefit of airport expansion has been increasingly counterbalanced by environmental concerns. Unrestricted capacity growth would impact those living around airports via increased noise and reduced air quality, and on the wider population via its contribution to climate change. However, restricting capacity growth can have significant national and global implications. Capacity constraints may lead to increases in airfares and airline network changes that take transit and origin-destination traffic away from the region, thus limiting growth in air traffic and the economy. London is a topical example. Airport capacity constraints at Heathrow may ultimately lead to a loss of London's hub status, which would almost certainly translate into negative direct, indirect and induced economic consequences for London and the UK economy as a whole. Hence, the UK Government is currently evaluating whether to add capacity to the system. Such capital-intensive airport capacity expansion decisions are being dealt with by many countries, not only in Europe and the United States, but also increasingly in developing markets. Countries stand to gain or lose economically depending on the performance of their major airports, particularly intercontinental transit hubs.

Airport capacity expansion decisions therefore need to be based on rigorous scientific models that simulate passenger and industry behaviour in an integrated way, as well as illustrate the economic and environmental implications of the various options. Developing such models is challenging because, while global air travel is expected to grow steadily over the next few decades, significant changes are expected in the global distribution and structure of traffic, with the expansion of emerging market economies and the development of new business models (e.g., alliances, low-cost long-haul airlines), marketing strategies (e.g., loyalty programs) and new technology (e.g., very long-range aircraft that will allow passengers to bypass intercontinental hubs). Furthermore, there is a high degree of uncertainty in the drivers of this change (e.g., future income and GDP levels, fuel prices), as well as the nature of the change itself. The tools currently used to assess the impacts of airport expansion policies are limited. Existing models (e.g., the DfT Aviation Model) do not take into account a number of critical factors affecting passenger choice of airports and airlines (e.g. air fare and loyalty programmes), and ignore airline competition for passengers. In addition, they deal with uncertainty only in the simplest way, typically using scenario-based analysis, and do not attempt to model future changes in system structure (such as the growth of low-cost long-haul carriers). We therefore propose to develop an adaptable, responsive model, which can rapidly assess both the beneficial and undesired impacts of airport capacity constraints and expansion, accounting for uncertainty at every level. This model, ACCLAIM, would build on the existing AIM framework, and add significantly to its capabilities by providing support to the multi-billion pound investment decisions at stake.

The proposed methodology is to integrate a global model of passenger itinerary choice (including airport and airline choice), as a function of travel time, fare, airline loyalty, airport access and cost, with a model of airline decision making, simulating airline fare, network, frequency and fleet decisions under competition. The resulting passenger and air traffic flows will then output to impact modules, estimating climate, air quality, noise and economic effects. Application of the tool will then be demonstrated in the context of airport capacity in London, simulating its impact on a national, regional and global scale.


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Description The research funded through this award has produced
(a) An understanding of the economic impacts of large transport infrastructures (e.g. high speed rail, airports). This will contribute to the policy debates in these areas.
(b) A database of air travel demand that will help us further probe into the drivers of air travel behaviour. This is expected to be useful to transport planners in the UK.
Exploitation Route We anticipate the following pathways
(a) Further academic research that builds on the academic outputs of this project, viz journal papers and conference presentations
(b) Further analysis of the data collected, by academics and planners - to draw additional insights into air travel behaviour
(c) Direct engagement of the research team with planning and regulatory bodies in the UK (DfT, CAA), to present the analysis and modelling results from this research project
Sectors Transport

Description The key outcome of this project has been the generation of a novel database and the wide-ranging analyses based on this data. This has broadly had two main impacts to date. First, the empirical analysis has identified COVID19 impacts on air travel demand, which has been a valuable contribution to workshops focused on recovery of the airline industry. In particular, the proceedings of a workshop organised by the US-National Academy of Sciences (details elsewhere in this submission), where our work was presented and discussed, has been widely downloaded all over the world. Second, the level of detail in the ACCLAIM air travel database, has served as valuable training for MSc students interested in a career in the air travel industry. To date two MSc students who worked with this data (2020 and 2021 cohorts) went on to start their careers in the air travel industry. Interest from the MSc students continues to grow, as we have 3 students working with this database currently (2022 cohort). Looking forward, we intend to widen our collaborations with academic colleagues internationally to make this data available for analysis by students. The data will also be appropriately archived within the UK Data Archive. In addition, the findings of the analysis to date (which ranges from covid impacts on air travel demand to environmental attitudes of air passengers to the spending habits and time use patterns of air passengers), will be shared with the industry through the UK Civil Aviation Authority (CAA).
First Year Of Impact 2021
Sector Education,Transport
Impact Types Policy & public services

Description Training MSc students for the airline industry
Geographic Reach Europe 
Policy Influence Type Influenced training of practitioners or researchers
Impact Two MSc students who entered the airline industry with appropriate training
Title Stated Preference Survey for Airline Passengers 
Description Novel survey questionnaire aimed at understanding travel related decisions made by airline passengers 
Type Of Material Improvements to research infrastructure 
Year Produced 2020 
Provided To Others? No  
Impact The survey questionnaire was used to collect an international dataset of airline passengers from four cities (London, NYC, Sao Paulo and Shanghai). 
Title ACCLAIM Air Travel Demand (AATD) Database 2019-2020 
Description Cross national database from London, New York City, Sao Paulo and Shanghai containing information about air travel behaviour and demand prior to and during the COVID19 pandemic. The data was collected during 2019-2020 through two waves of a survey, the first wave collected revealed preference data about an air travel episode in 2019, and the second wave collected stated preference data from the same sample in 2020 about their air travel itinerary choice. The second wave also included a COVID-specific stated preference experiment. The survey is unique in several aspects 1. It is the only cross national air travel demand dataset that we are aware of 2. It is one of the very few datasets that contains both revealed and stated preference data of air travel itinerary choice 3. It contains information about passenger attitudes and preferences with respect to the environmental impacts of air travel 4. It contains information about consumer attitudes with respect to the impacts of COVID19 on air travel 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
Impact The first of several papers, based on analysis of this data, was focused on the impact of COVID19 on air travel in the four cities, and was accepted for presentation and publication by the Transportation Research Board 100th Annual Meeting. On the back of this paper, the research team at Imperial was then invited to present our findings at a virtual workshop at the US National Academies of Sciences. We currently have 3 more papers in various stages of the publications process, and an active collaboration with Ricardo Daziano at Cornell University in the analysis of this data. 
Title Demand models using CAA data 
Description We developed several air passenger demand models using microdata from the CAA Departing Passenger Survey during 2017, and are currently continuing the model development. The early models are essentially discrete choice models of air passengers' choice of itinerary (time of day, class of travel, etc) as a function of socioeconomics (income, employment status). We are extending these models to include choice of airline as a function of historical performance including delays. 
Type Of Material Computer model/algorithm 
Year Produced 2018 
Provided To Others? No  
Impact No notable or direct impacts so far, but we are beginning to engage with the DfT/CAA on these models. Towards the latter part of 2018 these models will play a significant role in the integrated airline demand and supply model being developed by the UCL Energy Institute. 
Description CAA Passenger Demand Modelling 
Organisation Department of Transport
Department Civil Aviation Authority (CAA)
Country United Kingdom 
Sector Public 
PI Contribution The Imperial College research team brings our expertise in the disaggregate econometric modelling of passenger demand to this partnership. This expertise enables us to analyse and exploit the CAA data in a manner that is otherwise not within their means to do so. Our analysis of the CAA data will also enable the CAA to answer policy questions of particular interest to them.
Collaborator Contribution The CAA provides detailed (individual level) data from their Departing Passenger Survey - which is conducted on an annual basis at UK airports. While aggregate statistics from this survey are freely available on the CAA website, they have committed to sharing the microdata for 2007-2010 which if commercially acquired would cost at least 50,000GBP pa. The CAA also brings to this partnership their understanding of the aviation market, and an identification of the pressing needs of this market. Moreover, the CAA will support our survey administration strategy for the significant data collection task planned for summer 2018.
Impact The CAA passenger survey data was analysed as part of an MSc research project in 2017 to produce a distinction level MSc thesis. We are currently engaged in further analysing the data, and have written up a review paper on modelling air passenger demand, to be submitted to the Transport Reviews journal by end of 2020.
Start Year 2016
Description Ricardo Daziano 
Organisation Cornell University
Country United States 
Sector Academic/University 
PI Contribution Expertise in analysing air travel behaviour
Collaborator Contribution Expertise in stated preference survey design
Impact We have worked together to design a data collection exercise. The data is being cleaned, and curated. We anticipate a few key outcomes over the next 1-2 years: (a) a unique data source that will be a direct output of this project and available for research, (b) a journal paper about the design of surveys for air travel demand, and (c) models of air travel behaviour based on analyses of the dataset
Start Year 2019
Description Carbo and Graham, TRB 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation made at the 98th Annual Meeting of the Transportation Research Board, Washington DC, January 2019. The conference is attended by over 10000 participants including academics, industry representatives, planners and policymakers. The session which this presentation belonged to was attended by 50-100 people, and raised interesting methodological discussions
Year(s) Of Engagement Activity 2019
Description Committee Presentation at TRB 2019 & 2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk presented at a scientific committee meeting during the Annual Meeting of the Transportation Research Board. The committee meeting was attended by around 50 people, who were a mix of academics from a number of countries, planners from government agencies in the US, and transportation consultants from a number of countries. The talk sparked interesting discussions about the lack of data to understand air travel demand.
Year(s) Of Engagement Activity 2019,2020
Description Dialogue with CAA as an end user 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Third sector organisations
Results and Impact 5 people from the Civil Aviation Authority (CAA) attended a 2 hour presentation, which was focused on the type of statistical models and potential outcomes from this research project. This sparked questions and discussion about the value of such models to the CAA, which is the UK's specialist aviation regulator. The CAA, who also provided us with some of the early data used in this research project, are now keen to engage with our next stage of data collection and the resulting outputs.
Year(s) Of Engagement Activity 2017
Description International Transport Analysis Conference @ DfT 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact The UK Department for Transport, Environment and International Transport Analysis team, organised an International Transport Analysis Conference in November 2016. The aim of the conference was to commence a long term engagement between the DfT and academia, specifically with a view to engaging with academic research projects related to the maritime and aviation industries. I presented a brief summary of this research project, intended as a first step towards engaging more actively with the DfT, and had many interesting questions and strong interest in further engagement.
Year(s) Of Engagement Activity 2016
Description Presentation at a Virtual Workshop of the National Academies of Sciences, Engineering and Medicine 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Our conference paper submitted to the Transportation Research Board 100th Annual Meeting in January 2021, led to being invited by the US National Academic of Sciences to present our covid related analysis of air travel demand at a special workshop. The virtual workshop consisted of a primarily American panel, including academics, air industry representatives, representatives of air transport regulatory bodies; and our participation highlighted the value they perceived of the survey data collected as part of this EPSRC funded research project (and its subsequent analysis).
Year(s) Of Engagement Activity 2021