Vehicular communications in intelligent transporta-
tion system (ITS) promise to improve traffic efficiency, road
utilization, and safety. Achieving secure vehicular communica-
tions is vital for the deployment of vehicle-to-everything (V2X)
applications. This article provides a comprehensive overview of
physical-layer security (PLS) strategies employed for V2X. By
exploiting the randomness and the physical characteristics of
wireless channels, PLS offers reliable solutions against eaves-
droppers attacks as complementary approaches to cryptographic
techniques. We give a brief introduction to the architecture
and characteristics of V2X networks. Then, the fundamental
principles of PLS technology are proposed, followed by security
threats in V2X. Additionally, we discuss some open issues and
challenges for future research. Finally, we investigate a case study
where different challenges and technologies coexistence in one
V2X scenario.