Today, handsets and terminals are typically equipped with multiple radio interfaces. Meanwhile, various types of access networks using different radio technologies are being deployed all over the world. Also, there is a strong trend towards All-IP-Networks following the principle "Everything over IP", and "IP over everything". This development is leading researchers into the area of heterogeneous networking and overlay topologies.This paper focuses on mobility management issues related to such an environment supporting vehicular speeds of users using a policy-based approach and a network-layer metric for access network selection.A Mobile IP-based architecture is proposed where mobility bindings are sent periodically at a frequency depending on the speed of the user also taking variations in the network-layer metric into account and the overall signaling cost. The architecture is designed with a focus on minimizing packet losses and timely handling of vertical hand-overs.