Traditional project management tools are useful in managing design projects. However, incorporating ``soft data'' into tools like the critical part method (CPM) and bar charts is problematic. They are also best used for bottoms to top management and are, therefore, not very eective for macro managing projects. A system dynamic model can improve the current practices and reduce the problems in design projects when used as a tool for macro management. A model was developed for the management of detailed design process of a civil engineering project. The model consists of four interrelated subsystems: human resources, design production, controlling and planning. Two sets of data were used to test the model. Some policies and scenarios were then explored to gain insight into the model's behaviour and to seek alternatives for better management. The experimentation showed the following policy hierarchy. In terms of meeting scheduled time, the eectiveness of policies is in the order: (1) progress control, (2) manpower allocation, (3) estimation of workload and (4) realization of underestimated work. If the goal is to minimize labour-days expended or to reduce the cost of design, the eectiveness of policies is in the order: (1) manpower allocation, (2) progress control, (3) estimation of workload and (4) realization of underestimated work. As such, good project control and early perception of real progress are needed to ensure ecient resource allocation and on-time completion. This requires creation of a project organization which is able to recognize and process changing information on those issues.