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All passengers travelling by plane must follow the same route after reaching the departure terminal. First, they make their way to the aircraft, which is parked at its assigned boarding gate. When everyone has boarded the plane, it taxis through the airport towards the takeoff runways. When its turn comes, the aircraft accelerates rapidly down the runway, takes off and climbs to a high enough altitude to set off on its course.

These actions are determined by the system currently used to assign boarding gates, a system designed to minimize the distance passengers need to walk in the terminal. The system has its drawbacks. First, passengers must spend more time than necessary in the plane because take-off is not immediate: the aircraft needs to taxi from the terminal to its assigned runway. Second, the fact that the plane must move from one point to the other increases fuel consumption.

With these problems in mind, Ruperto Fernández, a doctoral student at the Department of Transport and Regional Planning, sets out a more sustainable alternative in his thesis. The researcher proposes a method for assigning boarding gates based on a broader perspective that takes into account more variables. The new system considers four factors: the distance passengers need to walk, the time it takes to move from place to place (including the time it takes for the aircraft to get to the runway), the cost for airlines, and the total cost for the system (which includes the cost for airlines and that borne by passengers).

When he reviewed studies on this subject, Ruperto Fernández noticed that none of them took into account the extra time passengers spend moving through the airport after boarding the plane. “It occurred to me that it might be better for passengers to walk for an extra two minutes if that would mean spending five minutes less inside the aircraft,” says Fernández.

He realized that the problem could be tackled using combinatorial methods: each aircraft could be assigned to a large number of gates with a different cost in each case. “To determine the optimal solution, the combination that results in the lowest cost, I used mathematical techniques and algorithms based on restrictions on assignment, that is, according to the number of gates each aircraft could be assigned to,” Fernández explains. When he applied his theoretical model to real operations at Barcelona Airport, the doctoral student found that airlines could save up to €50,000 a day by implementing the proposed system. They would also consume 24,500 liters less fuel each day, which makes the system a more sustainable and less-polluting alternative to the one currently used.

The doctoral thesis, supervised by Professor Francesc Robusté of the Department of Transport and Regional Planning, has won the 6th Abertis Research Award, given by the Abertis-UPC Chair. The prize, created in 2003, is aimed at promoting training and research related to the management of transport infrastructure.