Transportation planning in freight forwarding companies Tabu search algorithm for the integrated operational transportation planning problem Marta Anna Krajewska and Herbert Kopfer Chair of Logistics, University of Bremen, Wilhelm-Herbst-Strasse 5, 28359 Bremen {marta14,kopfer}@uni-bremen.de Summary. The integrated operational transportation planning problem extends the traditional vehicle routing and scheduling problem by the possibility of out- sourcing a part of the requests by involving subcontractors. The purpose of this paper is to present the integrated planning problem and to propose an approach for solving it by a tabu search heuristic. Existing approaches from literature which discuss vehicle routing combined with outsourcing regard only one specific type of subcontracting. This paper describes and explores the complex situation where an own fleet and several types of subcontracting are used for request fulfillment. As the approach contains new aspects, unknown to the literature so far, tabu search is extended to special types of moves. On the basis of computational results the cost structure is analyzed in order to investigate the long-term planning question whether and to what extend it is profitable to maintain an own fleet. Key words: freight forwarder, private fleet, subcontraction, tabu search, opera- tional planning 1 Introduction External procurement, also known as vertical division of work, means that a company purchases some items, such as vendor parts or services, from a third party (Grochla, 1980). However, the decision is not reduced to ‘either-or’ in the sense of ‘make-or-buy’ for each article or service within an isolated compari- son by predetermined criteria. Instead, the traditional ‘make-or-buy’ decision evolves into a reference analysis among the items involved (Wellenhofer-Klein, 1999). A major impact of such an analysis is noticed in the level and the struc- ture of costs in the outsourcing enterprise (Z¨ apfel, 2000). In particular, the ‘make-or-buy’ decision also applies to the transportation branch. Most freight forwarding companies reduce the capacity of their own vehicle fleet far under the varying total demand limit. Additional outside car- riers are involved in order to gain enough transportation resources for covering