The need for evaluation of ITS systems requires new modelling tools that allow a detailed modelling of both the roadside and the in-vehicle systems. One of the elements needed is a reliable longitudinal driver model. In this paper we outline the requirements of such a model and review the models that are available in the literature. We select the Helly car following model that was previously applied in the MIXIC simulation model as the most appropriate. We illustrate the use of the model by case studies from recent European projects and a Dutch project.