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This paper presents the design and development of an energy-efficient Risk Notification Message Dissemination Protocol (RNMDP) for vehicular ad hoc networks (VANETs). RNMDP propagates Risk Notification Messages (RNMs) from their location of origin (called the Risk Zone) to vehicles approaching the Risk Zone. A node receiving the RNM from another node waits for a Rebroadcast-Wait-Time before deciding to rebroadcast the message. The Rebroadcast-Wait-Time for a node is modeled based on the ratio of the distance between the node and the immediate sender of the RNM and the direction of movement of the node. Priority for rebroadcast is given for nodes farthest away from the sender and traveling towards the Risk Zone. If a node does not hear the RNM in its neighborhood during the Rebroadcast-Wait-Time, the node broadcasts the message in its neighborhood. A RNM is considered to have been delivered to all the vehicles in the road, if the message reaches the Target Zone. Simulation results indicate that RNMDP can achieve the same message delivery ratio as that of the commonly used flooding strategy at a significantly lower energy loss; but with a slightly larger delay (i.e., no more than 35% of the delay incurred for flooding). [ABSTRACT FROM AUTHOR]