Airport Surface Movement Optimization

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Taxiing aircraft contribute significantly to fuel burn and emissions at airports. The quantities of fuel burned as well as different pollutants, such as carbon dioxide, hydrocarbons, nitrogen oxides, sulfur oxides and particulate matter, are functions of aircraft taxi duration (along with throttle setting, number of running engines, and pilot and airline decisions regarding engine shutdowns during delays). The reduction of taxi times through improved planning of surface movements has the potential to reduce these emissions. Project 21 focuses on opportunities to reduce surface emissions through departure planning and surface movement optimization.

The research will include a detailed plan for implementing these techniques in a pilot study at an airport, with an overall goal of initiating wider adoption of the methods throughout the United States. This project will investigate approaches, such as gate-holds and taxi-route planning, to decrease taxi times. In addition, environmental factors will be incorporated into the objective functions of the optimization through the use of aircraft-specific delay costs, which will reflect the fact that the emissions characteristics of various aircraft may differ. Current baseline fuel burn and emissions at major airports will also be assessed in order to identify locations where the proposed strategies will produce the most benefits. Project 21 will also address the development of approaches to surface movement optimization that will balance both airport throughput and emissions objectives, while simultaneously ensuring fairness in the delays incurred by the different airlines. Barriers to the practical adoption of these approaches, such as gate usage and ownership issues, as well as surface infrastructure considerations such as taxiway layouts, the availability of tugs, and the presence and location of holding areas, will be identified, and possible approaches to overcome these barriers will be developed. Airline competition, tradeoffs between airline and air traffic control objectives, traffic flow management initiatives in the airspace and the presence of uncertainty in airport processes (which result in uncertain estimates of pushback times and taxi times) also pose significant challenges to surface movement optimization, and will be addressed.

Anticipated outcome

Plans and recommendations for ways to reduced surface emissions by optimizing aircraft surface movements. The results-to-date of this project are currently being transitioned to preliminary field tests of simple, low-risk strategies to decrease taxi times and emissions through mitigating airport surface congestion.

Participating universities

Massachusetts Institute of Technology

Lead investigator

Hamsa Balakrishnan, Assistant Professor, Deparment of Aeronautics and Astronautics, Massachusetts Institute of Technology,

Project manager

Christopher Dorbian
Steve Urlass (past program manager)


Demonstration of Reduced Airport Congestion through Pushback Rate Control, I. Simaiakis, H.Khadilkar, H. Balakrishnan, T. G. Reynolds, R. J. Hansman, B. Reilly and S. Urlass. Proceedings of the USA/Europe Air Traffic Management R&D Seminar, June 2011. Winner of Kevin Corker Award for Best Paper of ATM-2011.