In this paper, we present a decision support system (DSS) to optimize activities involving earth excavation, filling, hauling, recycling, and dumping in construction logistics projects. The system was designed through collaboration between operations research experts and a team at Strabag AG, an Austrian construction company. The DSS aids managers in scheduling construction activities by determining the amounts of materials that must be moved, purchased, recycled, and dumped in a given period, and by selecting paths that minimize the costs of performing these activities. Applying our DSS to the highway construction project, Autostrada Pedemontana Lombarda, has significantly improved the speed of decision making at Strabag AG and reduced its logistics costs by 10 percent. Our system, which is based on the use of linear programming, has two phases. In Phase 1, an aggregate mathematical model determines the feasibility of the project. In Phase 2, we execute a detailed model to determine the paths over which to move material in each period. We use graphical tools to visualize the model solutions and facilitate the decision-making process. The DSS, currently in use in several Strabag AG construction projects, is a powerful, flexible, and easy-to-replicate tool for solving construction logistics problems.