This paper deals with the evaluation to conduct during the iterative design of an ILE. During the design of an ILE a set of aspects of the system must be evaluated: usability, utility and acceptance; in this aim, a set of evaluation techniques already exists. For the design of the ITS AMBRE-add, several techniques were combined in order to evaluate and refine the system. In this paper, the approach we adopted to evaluate AMBRE-add is described and analysed in order to specify its contributions and its limits. Finally we propose a general approach of evaluation to be implemented during iterative design of an ILE.