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Programme

Abstracts and biographies of the keynote speakers Michael Pinedo and Johan Beumee can be found here.

Leendert Kok, “Vehicle routing under time-dependent travel times: the impact of congestion avoidance”

Daily traffic congestions form major problems for businesses such as logistics service providers and distribution firms. They cause late arrivals at customers and additional hiring costs for the truck drivers. The Dutch Organization for Transport and Logistics (TLN) estimated these additional hiring costs at 1.2 billion euro in the Netherlands in 2008. The additional costs of traffic congestions can be reduced by taking into account and avoid well-predictable traffic congestions within off-line vehicle route plans. In the literature, various strategies are proposed to avoid traffic congestions, such as selecting alternative routes, changing the customer visit sequences, and changing the vehicle-customer assignments. We investigate the impact of these and other congestion avoidance strategies in off-line vehicle route plans on the performance of these plans in reality. For this purpose, we develop a set of VRP instances on real road networks, and a speed model that inhabits the main characteristics of peak hour congestion. The instances are solved for different levels of congestion avoidance using a modified Dijkstra algorithm and a restricted dynamic programming heuristic. Computational experiments show that 99% of late arrivals at customers can be eliminated if traffic congestions are accounted for off-line. On top of that, almost 70% of the extra duty times caused by the traffic congestions can be eliminated by clever avoidance strategies.

Peter Hulshof, “Redesigning Ambulatory Care with a Doctor-travels-to-Patient Policy”

In many hospitals, ambulatory care is organized such that doctors remain in dedicated offices while patients come and go However, with demand for ambulatory care growing, it is becoming increasingly difficult to ensure that doctor offices, which double as consultation rooms, are located in easily accessible areas of the hospital. To overcome this, it may be advantageous to introduce flexible consultation rooms, and having patients wait in consultation rooms while care providers come and go. We compare the two approaches and show when a certain approach is better than the other. Additionally, we calculate the number of rooms required for a certain hospital setting.

Peter Vanberkel, “An exact approach for relating recovering surgical patient workload to the master surgical schedule”

No other department influences the workload of a hospital more than the Department of Surgery and in particular, the activities in the operating room. These activities are governed by the master surgical schedule (MSS), which states which patient types receive surgery on which day. In this paper we describe an analytical approach to project the workload for downstream departments based on this MSS. Specifically the ward occupancy distributions, patient admission/discharge distributions, and the distributions for ongoing interventions/treatments is computed. Recovering after surgery requires the support of multiple departments, such as nursing, physiotherapy, rehabilitation and long term care. With our model, managers from these departments can determine their workload by aggregating tasks associated with recovering surgical patients. The model, which supported the development of a new MSS at the Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, provides the foundation for a decision support tool to relate downstream hospital departments to the operating room.

Ove Göttsche, “Option Pricing and the Cost of Risk”

The problem of pricing and hedging options is well understood in the context of the Black-Scholes model. In this model, a perfect hedge is always possible, meaning, there exists a dynamic strategy such that trading in the underlying asset replicates the payoff of the option. However, the possibility of perfect hedge is restricted to certain models and restrictive assumptions. In more realistic models a perfect hedge is not possible and thus an option bears a residual risk that cannot be hedged away completely. Therefore, pricing an option consist of two parts: the cost of a hedging strategy that reduces the risk, and a premium to cover the residual risk. The talk will illustrate these differences by two simple models.

Fei Liu, “Assessment of Traffic Impact on Future Cooperative Driving Systems: Challenges and Considerations”

Currently, Dutch high way encounters two major difficulties: capacity and safety. Latest technologies are expected to contribute to solve the problems. Connect & Drive (C&D) is a start-up project to develop a cooperative driving system to improve the traffic performance on Dutch highways. It consists of two interactive subsystems: cooperative adaptive cruise control (CACC) and connected cruise control (CCC). In C&D systems, vehicles are able to communicate with each other and with the road side units (RSU). The information gathered from other vehicles and RSUs is used to help vehicles/drivers to learn the driving environment better and earlier, so that vehicles/drivers can make decisions and react on the disturbances on time. To assess the traffic performance of C&D systems, a traffic simulation model will be established for large-scale evaluation and providing feedbacks to system designs. This talk introduces the cooperative driving system and discusses the factors determining the traffic performance and the challenges to establish such a traffic simulation model.

Luc Wismans, “Dynamic Traffic Management Measures to Optimize Accessibility and Externalities: Effects of Single Objective Optimization”

The optimization of traffic systems by expanding or improving an existing network is often referred to as a Network Design Problem (NDP). The Optimization of dynamic traffic management (DTM) measures can be seen as a variant of the NDP. Traditionally, this type of optimization is focused on improving accessibility, given particular boundary conditions for traffic safety and livability (set by law). Yet, the quality of traffic systems is not only a matter of accessibility, but also of externalities such as traffic safety, air quality and climate. Recently, there has been an increase in the attention paid to these problems in our society, mainly in the context of climate and air quality, which are of increasing importance when policy decisions are made. This means a need for multi-objective optimization of traffic systems incorporating the externalities. There are more studies related to this subject; however, until now these studies have been limited to considering only a few externalities or are focused on local optimization. That is why the University of Twente started a research program to determine how regional traffic systems can be optimized using multiple objectives and traffic management measures taking traffic dynamics into account. This research is about solving the multi objective NDP in which minimizing the externalities of road traffic using DTM measures are the objectives. This presentation will focus on the results of research on optimization of DTM measures for single objectives concerning accessibility and externalities. Within this research the NDP problem is formulated as a bi-level optimization Problem. The formulation and calculation of the objective functions are discussed using a dynamic traffic assignment (DTA) model and three solution approaches are presented using genetic algorithms and compared in a case study. Furthermore, an analysis of objectives being opposite or aligned when a traffic system is being optimized using these measures is presented.