Aircraft Taxi-Out Emissions at Congested Hub Airports and Implications for Aviation Emissions Reduction in the United States

This paper will estimate the total aircraft taxi-out emissions over the course of a day at Newark Liberty International Airport. Departures currently have to wait up to 60 minutes to depart once they have pushed back from the gate, and most of this time is spent idling on the taxiways while emitting harmful pollutants into the atmosphere. A queuing model for aircraft waiting to depart was developed to test different emissions scenarios and was calibrated using data from the airport in August 2005, a peak travel month. These different scenarios include: (1) redistribution of flights over the course of the day, (2) fleet composition restructuring, and (3) variations in number of departures under current capacity. Each scenario's associated emissions benefits are computed. For instance, in an extreme case of redistributing departures evenly across flight hours of a day, a 43% emissions reduction from the base case scenario could be achieved. On the other hand, under a 2015 demand case of a 30% increase in departures, the emissions estimate increases by 50%. We conclude that emission reduction strategies addressing aircraft taxi-out emissions through congestion mitigation and fleet restructuring can lead to significant emissions benefits and play a critical role in meeting environmental challenges for future aviation.