###### Abstract  
With the continuous development of connected and automated vehicles (CAVs) and Internet of Vehicle (IoV) technologies, various application scenarios have put forward higher requirements for vehicular communications. On the one hand, applications related to vehicle driving safety require lower latency and higher throughput. On the other hand, users who use cellular vehicle-to-everything (C-V2X) to transfer data will have to face high communication fees due to the increasing amount of data. Therefore, from the perspective of balancing quality of service (QoS) and user communication costs, this paper integrates dedicated short-range communication (DSRC) and C-V2X, two vehicular communication technologies with their own advantages, into a framework called cluster-based traffic differentiated hybrid routing (CTDHR), to provide services for in-vehicle communication. A vehicle clustering method based on hierarchical clustering is proposed to solve problems (e.g., the communication linking being difficult to maintain and the frequent cell handover due to high-speed movement of vehicles). The CTDHR framework is modeled on the resulting clusters and an objective equation was established. Finally, since the obtained objective equation is a nonlinear integer programming problem, we propose a heuristic algorithm to solve this optimization problem. In the simulation experiments, CTDHR shows better communication performance than the existing DSRC and C-V2X hybrid models. The experimental results show that CTDHR can reduce the communication costs of users while satisfying QoS. The DSRC based on 802.11p, proposed by the IEEE research group [9], and the C-V2X based on the cellular network proposed by 3 GPP [10], have become the most likely vehicular communication technologies to be put into practical application. Studies and simulation experiments have shown that, compared with DSRC, C-V2X has better performance in terms of throughput, data transfer rate, and response time [11]. However, vehicular ad hoc networks (VANETs) based on DSRC have advantages in certain aspects. For example, the average delay of VANETs between single hops is only half of a C-V2X transmission; C-V2X needs to charge users due to the need to use the network service provider's infrastructure, but DSRC does not charge users for direct communication between vehicles; in addition, in areas with insufficient infrastructure, DSRC can be used as an effective blindness measure [12]. Therefore, DSRC has not been abandoned in both academia and industry and is still widely used in road warning, vehicle networking, and other fields. In recent years, many scholars have combined two vehicular communication technologies into one in-vehicle communication framework for research, achieving good results [13; 14; 15; 16; 17]. Combining DSRC and C-V2X into a framework will increase latency compared to using C-V2X alone, but this is beneficial in many aspects, such as reducing the occupancy rate of cellular network communication resources, reducing energy consumption, improving throughput, reducing communication costs for users, etc. [13; 14; 15]. Research on hybrid applications of DSRC and C-V2X can be divided into two categories. One is the hybrid when different vehicles are equipped with different communications equipment (that is, some vehicles are only equipped with C-V2X equipment, and some vehicles are only equipped with DSRC equipment) [17]. In this scenario, the data format needs to be changed continuously during communication, and the communication management is more complicated. The other category is the hybrid implementation in the scenario where all vehicles are equipped with both communication devices [13; 15; 16]. Compared with the former, the latter has stronger operability, so it has received more attention from researchers. It is worth noting that due to the high mobility of vehicles, it is difficult to maintain the vehicular communications link, and frequent cell switching is required when using C-V2X [12].