Stochastic Dynamic Models for Reducing Air Traffic Delays at Heathrow

Shone, Robert and Fairbrother, Jamie (2024) Stochastic Dynamic Models for Reducing Air Traffic Delays at Heathrow. In: EURO 2024 - 33rd European Conference on Operational Research, 2024-06-30 - 2024-07-03, Technical University of Denmark.

Abstract

Imbalances between demand and capacity at the world’s busiest airports cause air traffic delays, which can have serious financial and environmental consequences. The capacity of the runway system generally acts as the main bottleneck at congested airports. To alleviate the burden on runway capacity, various types of interventions are possible. At the pre-tactical stage (from a few days up to a few hours before a day of operations), the schedule can be adjusted by imposing ground delays on flights in order to avoid “hotspots” of delay occurring at peak times. At the tactical stage (during the day of operations itself), sequencing of take-offs and landings can be optimised in order to minimise average time separations between runway movements, which depend on aircraft weight classes. Academic researchers have developed various mathematical models for optimising these kinds of interventions, but few of the developed models consider both pre-tactical and tactical interventions within an integrated model. This talk will discuss the progress of an EPSRC-funded project (EP/X039803/1) aimed at integrating pre-tactical and tactical interventions in order to reduce air traffic delays at Heathrow Airport. We formulate a stochastic dynamic optimisation problem in which the “system state” at any given time includes hundreds of variables evolving via continuous-time stochastic processes. Solution approaches via approximate dynamic programming are possible in theory, but very difficult to implement in practice. Instead we consider an approach based on the emerging field of “simheuristics”, which involves continuously simulating possible trajectories of future random events and using a ranking and selection method to optimise runway sequences. In addition to this, hotspots of delay are identified and ground delays are imposed at regular intervals during the day in order to smooth out the pattern of demand over the course of the day. This work is in collaboration with NATS (https://www.nats.aero/), which provides air traffic control services to airports in the UK and around the world.