Applying Rational Unified Process (RUP) in a project means to develop a set of models before the system could be implemented. The models depict the essentials of the system from requirements to detailed design. They facilitate getting a system that has appropriate and rich documentation (therefore highly maintainable) and addresses user needs. However, creation of the models may cause overheads since a lot of work has to be put to elaborate the artefacts. In this paper a method that makes RUP more efficient is proposed. The method makes use of the fact that every subsequent model is developed basing on the previous model. In other words, models are successively transformed from requirements up to executable code. In particular, design model bases on an analysis model. The proposed method applies automatic model transformation from an analysis model to a design model. Firstly, an approach for performing automatic transformation is chosen. Secondly, a tool applying this approach is implemented. Finally, the transformation tool is tested and evaluated in an empirical study. The results show that automation of model transformation may be beneficial, and therefore can help in getting better systems in shorten time.