As climate change intensifies, urban transportation systems face unprecedented challenges requiring sophisticated analytical approaches. This chapter, written in the style of a “white paper,” examines how mathematical modeling provides essential tools for addressing the intersection of urban transportation planning and climate mitigation. Through optimization theory, network analysis, and equilibrium modeling, mathematics enables planners to quantify emissions, evaluate infrastructure investments, and design resilient systems. The integration of mathematical methods with climate science and urban planning represents a critical pathway toward sustainable urban mobility in the twenty-first century. We also present some unsolved problems.