In the absence of extensive real-world data on operational strategies and new mobility solutions, including automated vehicles and emerging mobility options, the adoption of modeling and simulation testbeds emerges as a pivotal tool for evaluation at scale. However, while there is a substantial body of research on modeling and simulating new mobility solutions, much of this work remains theoretical and disconnected from the practical needs of practitioners and policymakers. There is a critical need for more applicable, robust, and validated simulation testbeds that can bridge the gap between research and real-world applications. These testbeds should be designed to meet the specific requirements of practitioners and policymakers, enabling them to evaluate new mobility solutions effectively and make informed decisions to improve accessibility, efficiency and sustainability of transportation systems.