In modern economies it is essential a proper system of transport that enables population mobility and consequent accessibility to services. However, its current configuration is causing strong negative externalities and generates much of the problems of environmental, social and energetic sustainability. The changes required by the current unsustainable configuration have to be based on a new vision of transport and on the development of theoretical and empirical criteria that enable the creation of sustainable transport systems. The purpose of this study is to analyse the most important factors of urban mobility in its current configuration, but not only the mobility of passengers but of all the elements of mobility in urban environments. Externalities caused by transport have been analysed, and the necessary principles to develop a model to aid decision-making regarding the modal split in a city have been developed. From a holistic view, it has been developed an analytical model based on methodological support obtained from the technique of multi-criteria analysis AHP (Analytic Hierarchy Process), with the aim of achieving user satisfaction, sustainable growth and energetic and environmental efficiency. The construction of the model has allowed to analyse the sensitivity and robustness of the AHP, so as to obtain the classification of attributes with respect to an ideal situation, but also the most appropriate modal split of alternatives with respect to the various evaluation criteria. As operation check of the functioning made by the model, a methodology in a case study with different characteristics has been applied.