Today, the Controller Area Network (CAN) is a widely used in-vehicle network. However, due to the constraint of the theoretical upper bound speed of CAN, we proposed Scalable-CAN (SCAN), which employs round-robin scheduling to improve upper bound speed while keeping the compatibility with traditional CAN. Moreover, we proposed the worst-case response time (WCRT) analysis for a single SCAN bus system and showed the real-time performance.In this paper, to apply SCAN to a next-generation in-vehicle network composed of a SCAN bus and a CAN bus, we first propose a schedulability analysis method for the integrated network system. Second, we show its real-time performance and highlight the effects of the bandwidth extension and throughput performance of the SCAN integrated system. Finally, we conclude that SCAN achieves lower latency, high schedulability, and high integrity toward a next-generation in-vehicle network.