# Harmonized Autonomous-Human Vehicles via Simulation for Emissions Reduction in Riyadh City
## 6 Discussion
While specific traffic conditions may vary, the behavioral advantages of AV coordination such as reduced stops, smoother lane transitions, and lower emissions are broadly applicable. Furthermore, our study carries key policy implications that emphasize the importance of infrastructure preparedness, such as enabling V2X-compatible intersections and deploying roadside units (RSUs); policymakers may also consider incentive-based strategies, including subsidies for AV-enabled fleets and phased implementation along strategic corridors. Overall, the HARMONY-AV framework provides a flexible simulation approach to support data-driven mobility planning across the region. While direct field observation data for the selected corridor in Riyadh were not available at the necessary resolution, we grounded our simulation using official traffic counts from Saudi open data sources and congestion metrics from the TomTom traffic index. The resulting outputs, including average travel times and speed profiles, aligned closely with published regional norms. Although formal calibration against real-time field measurements was not feasible, the combination of validated datasets with statistical testing lends credibility to the findings and supports their relevance for practical urban mobility planning. It is also important to consider the real-world feasibility and cost implications of achieving high AV penetration rates, particularly the 50% scenario used in this study. While our simulations illustrate the potential benefits of such integration, actual deployment would require substantial investment in AV hardware (e.g., LiDAR, radar, onboard processing units) as well as supporting infrastructure such as roadside units (RSUs), V2X-enabled traffic signals, and robust wireless communication networks (e.g., 5G or edge computing). The costs associated with sensorized fleets and continuous network maintenance may pose financial and logistical challenges, particularly in regions where existing infrastructure is not yet digitally mature. Therefore, our 50% AV scenario should be viewed as a long-term planning benchmark rather than an immediate implementation goal. In practice, incremental adoption such as phased deployment along strategic corridors may offer a more feasible pathway to realizing the benefits of AV-human vehicle harmonization over time. In addition to simulation, the HARMONY-AV framework presents an opportunity for real-world application in Riyadh's evolving smart mobility ecosystem. Saudi Arabia's Vision 2030 and related initiatives led by entities such as the Royal Commission for Riyadh City and the Saudi Data and AI Authority (SDAIA) are already fostering advancements in digital infrastructure and data-driven urban management. The framework developed in this study aligns well with these goals, and could serve as a decision-support tool for evaluating AV integration strategies. Collaborations with local traffic authorities would be instrumental in refining the framework, helping to enable access to granular traffic data, pilot deployment zones, and validation platforms. Establishing such partnerships would also facilitate the gradual implementation of V2X infrastructure and policy development necessary for the safe and effective deployment of harmonized AV-HV traffic systems in Riyadh. It is worth noting that the selected corridor primarily includes signalized intersections and roundabouts, consistent with its role as a major arterial route within Riyadh; as such, our simulations did not incorporate uncontrolled intersections, which are more commonly found in suburban or residential areas. While this design choice reflects the operational realities of high-volume urban roads, it may limit the applicability of the results to less-regulated settings where vehicle behavior, right-of-wayambiguity, and AV decision-making challenges can be more complex.