Aligning barge and terminal operations using service-time profiles.

We consider a key issue in hinterland container navigation in ports, such as Rotterdam and Antwerp, namely the barge handling problem: how to optimize the alignment of barge and terminal operations in a port. We make a major step in solving the barge handling problem for practical settings. Specifically, we consider restricted opening times of terminals, unbalanced networks, the presence of sea vessels, and closing times of containers. Consequently, at a terminal a barge faces time dependency in: (1) the waiting time until the start of handling and (2) the handling time itself. The concept of waiting profiles which we introduced in an earlier paper only deals with (1). To deal with (1) and (2) together we introduce a more comprehensive concept, namely that of service-time profile. To establish how well our approach works, we evaluate the performance of our distributed planning approach extensively by means of simulation. We compare our results with those based on centralized planning by using an off-line benchmark resembling it. We show that the Multi-Agent system that we introduce enables barge and terminal operators to align their operations efficiently. Hence, it can be seen as a promising solution approach for solving the barge handling problem, since it enables (competing) companies to collaborate in a competitive way

The delivery dispatching problem with time windows for urban consolidation centers

This paper addresses the dispatch decision problem faced by an urban consolidation center. The center receives orders according to a stochastic arrival process, and dispatches them for the last-mile distribution in batches. The operator of the center aims to fi nd the cost-minimizing consolidation policy, depending on the orders at hand, pre-announced orders, and stochastic arrivals. We present this problem as a variant of the Delivery Dispatching Problem that includes dispatch windows, and model it as a Markov decision problem. For toy-sized instances, we solve this model to optimality. Through numerical experiments on these instances, we show that we approximate the optimal values with an error of less than 2%. Larger instances suff er from intractably large state-, outcome-, and action spaces. We propose an Approximate Dynamic Programming (ADP) algorithm that can handle such instances, using value function approximation to estimate the downstream costs. To cope with large action spaces - with sizes up to 2120 in our experiments - we formulate an integer linear program to be used within our ADP algorithm. To evaluate the performance of our ADP policies, we test against various benchmark policies, including a lookahead policy based on scenario sampling. We test the performance of ADP on a variety of networks. When the dispatching problem provides su fficient fl+6exibility in dispatch times, ADP outperforms our myopic benchmark policies by more than 15%, and lookahead policies by over 10%

A dynamic programming heuristic for vehicle routing with time-dependent travel times and required breaks.

For the intensively studied vehicle routing problem (VRP), two real-life restrictions have received only minor attention in the VRP-literature: traffic congestion and driving hours regulations. Traffic congestion causes late arrivals at customers and long travel times resulting in large transport costs. To account for traffic congestion, time-dependent travel times should be considered when constructing vehicle routes. Next, driving hours regulations, which restrict the available driving and working times for truck drivers, must be respected. Since violations are severely fined, also driving hours regulations should be considered when constructing vehicle routes, even more in combination with congestion problems. The objective of this paper is to develop a solution method for the VRP with time windows (VRPTW), time-dependent travel times, and driving hours regulations. The major difficulty of this VRPTW extension is to optimize each vehicle’s departure times to minimize the duty time of each driver. Having compact duty times leads to cost savings. However, obtaining compact duty times is much harder when time-dependent travel times and driving hours regulations are considered. We propose a restricted dynamic programming (DP) heuristic for constructing the vehicle routes, and an efficient heuristic for optimizing the vehicle’s departure times for each (partial) vehicle route, such that the complete solution algorithm runs in polynomial time. Computational experiments demonstrate the trade-off between travel distance minimization and duty time minimization, and illustrate the cost savings of extending the depot opening hours such that traveling before the morning peak and after the evening peak becomes possible