Several members of the Centre for Transport and Logistics (CENTRAL) attended the Institute of Mathematics and Operational Research Society conference on Mathematics in Operational Research held at Aston University in Birmingham last month. As part of this conference, Professor Konstantinos Zografos also led sessions on “Optimization of Airport Slot Scheduling Decisions”. Please see the end of this article for the title and author information of each of the talks mentioned.

Professor Konstantinos Zo.grafos organised a session in which Fotis Katsigiannis, Rob Shone and Jamie Fairbrother presented on the optimisation of airport slot scheduling decisions. This work is related to the EPSRC-funded project "Mathematical Models and Algorithms for Allocating Scarce Airport Resources (OR-MASTER)".

• Fotis's talk addressed the importance of incorporating the values of slots in airport slot scheduling decisions. The development of a slot valuation index (SVI), reflecting the preferences of the stakeholders involved in the slot coordination process, can overcome the limitations of existing methods which assume that `a slot is a slot' and fail to recognise that some slots may be more desirable to airspace users than others. Further work in this area will involve the collection of preference data from stakeholders in order to attach appropriate valuation weights to different slots.
• Rob's talk was concerned with optimising the trade-off between scheduling and operational delays at congested airports. The motivation for this work is to highlight the limitations of slot allocation methods which do not take into account the impact of stochastic effects on flight delays, and to propose a novel solution approach based on stochastic programming in order to model uncertainty in a more sophisticated way. Initial experimental results suggest that significant reductions in flight delays may be achievable without displacing flights by excessive amounts from their requested operation times.
• Jamie's talk addressed the scheduling of series of slots using segmentation methods. Scheduling slots in series is generally more restrictive than scheduling for individual days, and the resulting slot allocations can be quite unsatisfactory to airspace users (especially 'new entrants' to the slot allocation procedure). To overcome this, two different approaches are possible: (i) changing the threshold for slot requests to be allocated as a series; (ii) promoting greater flexibility by allowing requests to be scheduled at different times on different `segments' of the scheduling season.

Professor Zografos also organised a session on the optimisation of electric vehicle operations in which Seyma Bekli made two presentations on one-way electric car-sharing systems (OWECS). OWECS is a car rental system for short time period rents between two stations that are not necessarily the same. Although this system may attract the commuters in urban areas, it has some major drawbacks such as accumulation/shortage of vehicles at some stations or charging durations of vehicle batteries.

• The first study presented (work of Dr. Burak Boyaci and Prof. Konstantinos Zografos) focuses on a framework that investigates the effects of incentives that are given to changes in stations and time of the trips on the daily profit and number of relocations (redistribution) of the vehicles done by personnel. The proposed framework suggests that up to 15% increase in profit, and 80% decrease in the number of relocations could be achieved.
• The second study focuses on optimally implementing fast chargers to the stations, while maximising the profit. In order to increase the efficiency of the system, charger switches are taken into consideration. Preliminary results show that the profit could be increased significantly by adding fast chargers to the system, and if the switches are allowed, a higher profit could be obtained.

In addition to the above sessions, Professor Kevin Glazebook and Luke Rhodes-Leader also led sessions on themes as below:

• Professor Kevin Glazebrook lead a session on application optimisation in which David Torres Sanchez gave a talk in the "Applications of Optimisation" stream. The focus was aviation, particularly on airline fleet maintenance scheduling for multiple airlines with tail assignment. The talk presented a framework to combine the two problems efficiently in order to cope with the dimensions introduced by considering a long-term planning horizon.
• Luke Rhodes-Leader gave a presentation about combining integer programming and simulation optimisation to come up with rescheduling options for airlines following a disruption to their schedule. Whilst this problem has been studied before, there are not many approaches that account for the uncertainty inherent in the airline industry. This is where the simulation plays a part to test and improve solutions suggested by the deterministic integer program. Empirical results are promising and appear to reduce costs associated with a disruption.

The conference provided an excellent opportunity for LUMS colleagues to demonstrate their research strengths, and network with the considerable community of researchers and practitioners who were in attendance.

Presentations and Authors

• Fotis's talk was entitled "Incorporating the value of slots in airport slot scheduling decisions", authored by Fotis Katsigiannis and Konstantinos Zografos.
• Rob's talk was entitled "Optimising the trade-off between scheduling and operational delays at congested airports", authored by Rob Shone, Jamie Fairbrother, Kevin Glazebrook and Konstantinos Zografos.
• Jamie's talk was entitled "Optimum Scheduling of Series of Slots with Scheduling Season Segmentation", authored by Jamie Fairbrother and Konstantinos Zografos.
• Seyma's first talk was entitled "Introducing Partial Customer Based Vehicle Relocation in one Way Electric Carsharing Systems", authored by Burak Boyaci and Konstantinos Zografos.
• Seyma's second talk was entitled "Implementing Fast Chargers to One-way Electric Carsharing Systems", authored by Seyma Bekli, Burak Boyaci and Konstantinos Zografos.
• Luke's talk was entitled "Airline Disruption Management using Multifidelity Simulation Optimisation", authored by Luke Rhodes-Leader, Stephan Onggo (Southampton), David Worthington, Barry Nelson (Northwestern University) and Richard Standing (Rolls-Royce).
• David's talk was entitled "An Optimisation Framework for Airline Fleet Maintenance Scheduling and Tail Assignment", authored by David Torres Sanchez, Burak Boyaci and Konstantinos Zografos.