In vehicular ad hoc networks (VANETs), because of the nonexistence of end-to-end connections, it is essential that nodes take advantage of connection opportunities to forward messages to make end-to-end messaging possible. Thus, it is crucial to make sure that nodes have incentives to forward messages for others, despite the fact that the routing protocols in VANETs are different from traditional end-to-end routing protocols. In this paper, stimulation of message forwarding in VANETs is concerned. This approach is based on coalitional game theory, particularly, an incentive scheme for VANETs is proposed and with this scheme, following the routing protocol is in the best interest of each node. In addition, a lightweight approach is proposed for taking the limited storage space of each node into consideration.