Intelligent Transportation Systems have a variety of application, from improving transportation safety and traffic management to infotainment. The development of these systems includes the deployment in the vehicle of sensors that collect data and share them with actors having different profiles, roles and motivations. These data may concern the private life of drivers, who, most of the time, are not aware of the recipients and of the usage of their data. A key issue is to give to drivers control of their data. For that purpose, we propose in this paper a flexible and fine-grained access control policy of data, based on Attribute-Based Encryption, designed to protect drivers privacy. We also provide a description of the security architecture to enforce such an access control.