Airport Capacity Consequences Leveraging Aviation Integrated Modelling (ACCLAIM)

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.

The ACCLAIM systems model will enable more informed policy decisions to be made by balancing the various costs and benefits of airport capacity and environmental policies and thus addresses all three impact dimensions, i.e., fostering economic performance, increasing the effectiveness of public policy, and enhancing quality of life. The Airports Commission write that ACCLAIM, "could be a highly valuable tool", while the CAA write that ACCLIAM could be "highly valuable for policymakers and the aviation industry". The DfT write that "the ACCLAIM proposal appears to offer the potential of developing the available evidence base including consideration of issues such as airline decision making and competition - areas where the current evidence base and models are relatively less well developed." Sustainable Aviation, which "has a strong interest to see a more robust independently researched knowledge base to ensure informed decision-making by government and appropriate responses by all branches of the UK sector", write that "the ACCLAIM model can bring this evidence to the table". Finally, the AEF write that "ACCLAIM can make a unique contribution by taking a holistic approach that examines the interdependencies between issues (unlike existing models that address the individual impacts in isolation)."

Multiple paths will be pursued to maximise stakeholder benefit. In addition to disseminating results through the already existing website, conference presentations, publications, and existing networks (Sustainable Aviation, Greener-by-Design, World Economic Forum, etc.) will be exploited. ACCLAIM will also assemble an advisory board with six key stakeholder representatives from government, industry, and NGOs at the beginning of the grant lifecycle. The advisory board meetings will provide an important avenue to interact directly with industry and government, and to ensure that the direction of the research is consistent with their needs. Furthermore, the DfT will send a researcher to UCL and Imperial College on secondment to spend some time with the research teams at each respective institution, acting in an advisory role, and facilitating the dissemination of lessons learnt back to the DfT.

ACCLAIM will also organise three stakeholder workshops, which serve as milestones and as a vehicle to disseminate results to and receive feedback from stakeholders to refine the analyses. Other impact activities will also be investigated, including the development of web video clips and the use of social media. A dissemination strategy will be developed through discussions with the advisory board and stakeholders about the most appropriate formats for output and the most appropriate routes for dissemination. A key targeted stakeholder will be the general public, because of the interest and relevance of aircraft capacity expansion in London to the general population.

Collaboration with complementary projects is also planned. For example, continued collaboration is envisioned with the US PARTNER consortium in terms of individual work visits, joint workshops, data exchange and model comparisons.