Abstract
On a general basis, it is necessary to know the future traffic that will use the new toll motorway in order to calculate the social and economic profitability of the project. Therefore, a mixed model of generation and modal split was formulated. It will consider not only the transferred travellers from the rest of the infrastructures but the new ones. This ad-hoc model proposed in this study has been successfully validated in the corridor Madrid-Seville with the AVE (High Speed Train) implementation. Likewise, the validation has revealed the shortcomings of most data bases employed in interurban traffic studies as well as the possible effects of these shortcomings on the calculation of induced traffic.