## Reoptimization Gaps versus Model Errors in Online-Dispatching of Service Units for ADAC

Please always quote using this URN: urn:nbn:de:0297-zib-7928
• Under high load, the automated dispatching of service vehicles for the German Automobile Association (ADAC) must reoptimize a dispatch for 100--150 vehicles and 400 requests in about ten seconds to near optimality. In the presence of service contractors, this can be achieved by the column generation algorithm ZIBDIP. In metropolitan areas, however, service contractors cannot be dispatched automatically because they may decline. The problem: a model without contractors yields larger optimality gaps within ten seconds. One way-out are simplified reoptimization models. These compute a short-term dispatch containing only some of the requests: unknown future requests will influence future service anyway. The simpler the models the better the gaps, but also the larger the model error. What is more significant: reoptimization gap or reoptimization model error? We answer this question in simulations on real-world ADAC data: only the new model ZIBDIP{\footnotesize dummy} can keep up with ZIBDIP.

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Author: Benjamin Hiller, Sven O. Krumke, Jörg Rambau ZIB-Report ADAC ; high load; online ; optimality gap ; real-time ; soft time windows ; vehicle dispatching 90-XX OPERATIONS RESEARCH, MATHEMATICAL PROGRAMMING / 90Bxx Operations research and management science / 90B06 Transportation, logistics 2004/05/25 ZIB-Report (04-17) The rev. vers. appeared in: Electronic Notes in Discrete Mathematics Vol. 18, 1 December 2004, 157-163. The final vers. appeared in: Discrete Applied Mathematics 154 (2006) 1897-1907

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