The Vehicle Routing Problem for Aerial Firefighting

Abstract

Optimizing the routes of firefighting aircraft can reduce the time it takes to contain wildfires and make sure they remain within control. In this paper, a novel formulation of the Vehicle Routing Problem (VRP) is developed to improve aerial firefighting operations by optimizing aircraft routes. The formulation is a capacitated split delivery multi-trip VRP with time windows and hierarchical objectives. The primary objective is to minimize the time of carrying out all requested drops, and the secondary objective is to minimize the total flight time. Two types of aircraft are used: Scoopers and tankers. The main difference is that scoopers can refill their water tank from a water body. By easily adjusting the capacity and speed of the aircraft, most firefighting aircraft can be modelled using these two types, including helicopters. The program allows the user to input the number and types of aircraft available, the locations of airfield, fires, and nearest water body, intensity of each fire, and more. Several random cases and case studies were solved within the expert-recommended time limit of 5 minutes, yielding reasonable optimized routes. The problem is scalable and sizes ranging from one to 80 drops were tested and solved within 22 minutes. Furthermore, given a certain fire situation, the model can be simulated with various aircraft combinations to gain insights into fleet optimization. In one case study, it was demonstrated that replacing a scooper with a tanker can result in halving the total operation time. Strategic fleet planning is also demonstrated in a case study with the use of a Monte Carlo simulation, in order to compare the performance of different fleet options for a given setting. Therefore, the model is not only applicable in live situations, but can also be used as a supportive tool in planning for upcoming fire seasons, or reviewing and learning from past fires