With development of smart car, we expect there are many requests of various services to improve transport safety, relieve traffic congestion, reduce air pollution, and enhance the comfort of driving. However, the capabilities of vehicles are limited to store and compute large amounts of safety or non-safety related data. To deal with the requests, the importance of central cloud and roadside cloud will be increased. In this paper, we propose the optimal vertical handoff (VHO) in a cloud-based vehicular network setting. We show that VHO decision-making minimizes the time and cost at lower speeds, whereas it would be better not to perform VHO and only use central cloud system at higher speeds in cloud-based vehicular network. Furthermore, we suggest relay node selection protocol wherein the node selection is done on the basis of a link-stability. Finally, we show that the expanding of the coverage of roadside cloud helps the service drop rate at local cloud system.