###### Abstract  
The potential for an intelligent transportation system (ITS) has been made possible by the growth of the Internet of things (IoT) and artificial intelligence (AI), resulting in the integration of IoT and ITS--known as the Internet of vehicles (IoV). To achieve the goal of automatic driving and efficient mobility, IoV is now combined with modern communication technologies (such as 5G) to achieve intelligent connected vehicles (ICVs). However, IoV is challenged with security risks in the following five (5) domains: ICV security, intelligent device security, service platform security, V2X communication security, and data security. Numerous AI models have been developed to mitigate the impact of intrusion threats on ICVs. On the other hand, the rise in explainable AI (XAI) results from the requirement to inject confidence, transparency, and repeatability into the development of AI for the security of ICV and to provide a safe ITS. As a result, the scope of this review covered the XAI models used in ICV intrusion detection systems (IDSs), their taxonomies, and outstanding research problems. The results of the study show that XAI though in its infancy of application to ICV, is a promising research direction in the quest for improving the network efficiency of ICVs. The paper further reveals that XAI increased transparency will foster its acceptability in the automobile industry. intelligent connected vehicle; intrusion detection; safety; security; XAI +
Footnote †: journal: Medical Engineering  
The CAR 2 CAR Communication Consortium members build their C-ITS deployment plans on the cooperative vehicle to \"other things\" (V2X) short-range communications that perform everywhere at any time via local ad hoc networks in the 5.9 GHz band. This cooperative V2X (C-V2X) communication uses the European standard ETSI ITS G5 [7] which is based on the US market IEEE 802.11p WLAN standard specially designed for automotive applications in addition to the WAVE/DSRC, and long-term evolution-advanced (LTE-A) delivering quality of service for most V2X applications [8]. The successor standard, IEEE 802.11 bd, offers improved performance and seamless evolution of the radio technology which ensures efficient use of the allocated spectrum, and continuous operation of implemented services [4; 9]. Cooperative V2X systems in vehicles analyze the data received and warn the driver against dangers. By this principle, critical road safety situations and resulting accidents can be avoided [7]. The performance requirements for basic road safety and advanced V2X services are adapted from [10] and summarized in Table 1.  
To meet the demands of efficient connectivity of ICVs (awareness driving, sensing driving, and cooperative driving), the authors in [11] proposed the introduction of the sixth generation (6G) to compensate for the inability of the existing 5G to guarantee the best connectivity for fully autonomous connected vehicles as corroborated by [10]. Moreover, manually driven vehicles profit from cooperative V2X as well as all levels of assistance and automation up to fully self-driving cooperative automated vehicles [12]. Services such as providing information about traffic light signal phases and their predicted changes or barriers on the route in real-time furthermore support smooth and comfortable traveling [12]. By avoiding strong accelerations/decelerations, the fuel/energy consumption of vehicles can be reduced with favored effects on lowering noise and emissions. Sophisticated sensors of vehicles and in road infrastructure are able to detect other road participants [5]. However, common issues of ITSs include but are not limited to: (a) vehicle routing, (b) demand forecasting, (c) traffic prediction for flow and location, (d) processes optimization, (e) arrival time forecasting, and (f) anomaly or intrusion detection [13]. This survey is delimited to the state-of-the-art progress of XAI applications in solving the intrusion detection and mitigation issues of ICV networks.