Transportation systems are entering a transformative era shaped by the convergence of autonomous and connected mobility, green energy technologies, artificial intelligence, and smart-city infrastructure. This integration is expected to deliver safer, cleaner, more efficient, and more inclusive mobility while addressing critical pressures arising from climate change, rapid urbanization, and resource constraints. This chapter provides a comprehensive overview of future intelligent transportation systems (ITS), emphasizing the co-evolution of autonomy, connectivity, and low-carbon energy ecosystems within data-driven smart cities. Core enabling technologies—perception and sensing, V2X communications, edge–cloud computing, and AI-based decision-making—are discussed alongside system-level developments such as electrified mobility, renewable-energy-enabled charging networks, and multimodal integration including shared mobility and unmanned aerial vehicles (UAVs). Beyond technical progress, the chapter examines ethical, legal, and governance challenges that will shape deployment, including safety assurance, accountability, cybersecurity, privacy, and algorithmic fairness. Finally, a forward-looking research agenda and implementation pathways are proposed, with particular focus on resilience, equity, and scalable adoption across diverse socio-economic contexts. The chapter thus bridges technology, policy, and societal considerations to support the development of sustainable, intelligent, and human-centered mobility for future smart cities.