Blockchain security for smart transportation investigates how distributed ledger technology can strengthen trust, safety, and data integrity in intelligent transport systems (ITS) and connected vehicle environments. Research papers in this domain focus on applications such as secure vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication, decentralized traffic management, autonomous vehicle coordination, and fraud-resistant ride-sharing or logistics platforms. Blockchain ensures tamper-proof recording of vehicular data, protecting against threats like data manipulation, spoofing, Sybil attacks, and denial-of-service attempts that could disrupt transportation networks. Studies also explore how smart contracts enable automated toll collection, insurance claims, and mobility-as-a-service (MaaS) operations while enhancing transparency and efficiency. Key challenges such as scalability, real-time responsiveness, interoperability across heterogeneous systems, and privacy preservation are addressed through lightweight consensus mechanisms, edge–blockchain integration, and privacy-enhancing cryptography. Overall, research in this area highlights blockchain’s potential to secure next-generation smart transportation systems by providing resilience, accountability, and trust in highly dynamic mobility networks.