In the last decade, there has been an increasing body of research in dynamic vehicle routing problems. This article surveys the subclass of those problems called dynamic pickup and delivery problems, in which objects or people have to be collected and delivered in real time. It discusses some general issues as well as solution strategies.

We consider online routing optimization problems where the objective is to minimize the time needed to visit a set of locations under various constraints; the problems are online because the set of locations are revealed incrementally over time. We make no probabilistic assumptions whatsoever about the problem data. We consider two main problems: (1) the online Traveling Salesman Problem (TSP) with precedence and capacity constraints and (2) the online TSP with m salesmen. For both problems we propose online algorithms, each with a competitive ratio of 2; for the m-salesmen problem, we show our result is best-possible. We also consider polynomial-time online algorithms as well as various generalizations of our results. 1

We study the usefulness of lookahead in online server routing problems: if an online algorithm is not only informed about the requests released so far, but also has a limited ability to foresee future requests, what is the improvement that can be achieved in terms of the competitive ratio? We consider several online server routing problems in this setting, such as the online traveling salesman and the online traveling repairman problem. We show that the influence of lookahead can change considerably depending on the particular objective function and metric space considered.

customers may both receive and send goods, are an

Abstract not found

Vehicular Ad Hoc Networks (VANETs) are composed of vehicles equipped with advanced wireless communication devices. As a paradigm of decentralized advanced traveler information systems (ATIS), VANETs have obtained interests of researchers in both communication and transportation fields. The research in this chapter investigates several fundamental issues, such as the connectivity, the reachability, the interference, and the capacity, with respect to information propagation in VANETs. The authors ’ work is distinguished with previous efforts, since they incorporate the characteristics of traffic into these issues in the communication layer of VANETs; this mainly address the issue of the interference. Previous efforts to solve this problem only consider static network topologies. However, high node mobility and dynamic traffic features make the interference problem in VANETs quite different. To investigate this problem, this chapter first demonstrates the interference features in VANETs incorporating realistic traffic flow features based on a validated simulation model. Then, analytical expressions are developed to evaluate the interference under different traffic flow conditions. These analytical expressions are validated within the simulation framework. The results show that their analytical characterization performs very well to capture the interference in VANETs. The results from this work can facilitate the development of better algorithms for maximizing throughput in the VANETs.

Abstract not found