Recent years have seen a fast growth of video on-demand (VOD) services over HTTP. In order to improve service quality, video services are required to support different network conditions. For vehicular environments, this study proposes a novel adaptation method that improves quality of experience (QoE) by 1) reducing the number of bitrate switches and 2) avoiding sudden quality changes. The experiment shows that proposed method can provide a smooth video even under highly fluctuating network conditions.