Vehicular Delay-Tolerant Networks emerge as a vehicular networks technology that can be deployed on a wide range of scenarios. For example, it can be applied in sparse and remote regions characterised by sparse connectivity to allow data communications, as well as in urban scenarios. Frequent network partitioning, intermittent connectivity, long propagation delays, high error rates and short contact durations characterise these environments. To overcome some of these issues, cooperation approaches should be considered to force nodes to share their own resources. It is important to perform this task because nodes may be unwilling to cooperate due to a selfish behaviour. Selfish nodes affect considerably the func- tionality and the performance of the overall network. This paper overviews the most relevant contributions on cooperation for vehicular networks. It also proposes four different cooperation strategies for Vehicular Delay-Tolerant Networks and studies their impact on the performance of the network. These strategies are enforced on two delay-tolerant networks rout- ing protocols (Epidemic and Spray-and-Wait). Across all the experiments, it was shown that all the strategies contribute to the improvement of the overall network performance by increasing the bundle delivery probability and consequently decrease the bundle average delivery delay.