In vehicular ad-hoc networks, high mobility tends to break established paths and cause bandwidth waste because of path reconstruction. To improve the situation, this study presents a new position-based protocol. The new protocol uses control packets to collect approaching-the-junction information and, based on the information, lets moving vehicles adapt their routing paths dynamically when arriving at a junction. Compared with existing protocols which pre-store massive routing paths in a vehicle, the protocol can accurately relay packets to the destination by significantly reduced control packets. Transmission efficiency is therefore enhanced. Performance evaluation exhibits that the proposed protocol is suitable for practice in highly topology-changing vehicle-to-vehicle environments because it can accurately select targets for packet relay at less routing and storage cost.