This dataset provides the simulation-based results for Figure 10 of the discussion paper "Urban Transport Policies and Emission Reduction Strategies in Riyadh: Insights from a Multi-Agent Simulation" (2026). It compares the base case against a scenario in which average metro station access speed increases from 5.4 km/h to 10 km/h, representing improved first- and last-mile connectivity. Results show a reduction of 1.07 million tonnes of CO₂ per year, a 20% decrease in average travel time, and a modal shift of over 24,000 car users to public transport.