Please refer to the response to "Hardware-in-the-loop testbed expectations". Mainly, 2) Hardware-in-the-loop simulation testing is required in Phase I to demonstrate the feasibility of the architecture, critical components, and evaluate the benefits in traffic congestion mitigation under different scenarios. Virtual-only simulation may be acceptable where the proposed architecture is purely software- or firmware-based; however, the selected simulation approach should still credibly demonstrate system functionality and performance under representative conditions consistent with the Phase I objectives.