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Abstract: This study investigates the routing problems of road resurfacing in Taiwan''s smooth road project, incorporating multiple treatments served by different construction machinery in a way that propagates extra time window constraints to ensure that a subsequent treatment starts after the required preceding treatment has started or been completed. The routing problem is modeled as a multi-treatment capacitated arc routing problem with time windows (MTCARPTW) in order to determine a set of trips at a minimum total cost that covers all required links of road resurfacing work. The MTCARPTW is first transformed into a traveling salesman problem (TSP); then, a heuristics method based on ant colony optimization (ACO) is applied and evaluated based on the set of given circumstances. The computational results indicate that the proposed algorithm is efficient. This research contributes to identifying a new routing problem, modeling this MTCARPTW, and introducing the ACO to solve the problem efficiently. [Copyright &y& Elsevier]

Abstract: This study formulates the dispatching operations of ready mixed concrete (RMC) trucks as a job shop problem with recirculation, which includes time windows and demand postponement, as well as the external cost of transport, in a multi-objective programming model. This investigation divides factors that affect truck dispatching of RMC plants into intrinsic and imposed constraints, where intrinsic constraints refer to limits that must be satisfied during the concrete distribution process; imposed constraints are those that should be fulfilled to the greatest extent possible during dispatching. The results will help concrete plant dispatchers of small to medium-sized enterprises (SMEs) determine a cost effective and reliable day-to-day distribution scheme and achieve better customer service. This work contributes to both modeling and dispatching operations of RMC trucks as a job shop problem by applying optimization tools that enable RMC SMEs to detect and subsequently take advantage of opportunities that may exist for improving daily operation efficiency. [Copyright &y& Elsevier]