Device-to-Device (D2D) communications in 5G enabled vanet Networks offer significant advantages in terms of improved communication efficiency and reduced latency. However, ensuring secure and efficient key agreement among devices remains a critical challenge. In this study, we present a novel lightweight framework for D2D communications that addresses these concerns by employing a Signcryption-based key agreement scheme [1]. The proposed scheme is built on the foundation of Diffie-Hellman Hyper Elliptic Curve Cryptography and leverages two one-way cryptographic hash functions to enhance security. By integrating the signcryption technique, our framework achieves a seamless combination of encryption and signing [2], reducing computational overhead and conserving network resources in resource-constrained 5G-enabled devices. Furthermore, we prioritize user location privacy in our framework by employing advanced techniques, including the Chinese Remainder Theorem. This ensures that location information is protected and not exposed to unauthorized parties during D2D communication sessions. Through extensive simulations and performance evaluations using ns3, we demonstrate the effectiveness and efficiency of our proposed key agreement scheme for D2D communications in 5G enabled vanet Networks. The results show improved communication performance and reduced resource consumption, making our framework a promising solution for secure and efficient D2D interactions in the context of evolving 5G networks.