Heterogeneous networks allow mobile terminals to take advantage of complementary radio technologies for their concurrent connections. In this paper, the authors propose a mechanism for automated radio access network selection with several novelties: it enables terminals to build prioritized lists of target access networks independently for each of their active connections. It aims to satisfy user preferences. Lastly, it operates with two decision-making points (mobile terminal and core network), splitting the complexity of the overall process. After discussing the functionality of the proposed mechanism, they present its formal specification in SDL. Finally, a test-bed implementation comprising two access networks is presented.