  The increasing demand for emerging mobility systems with connected and
automated vehicles has imposed the necessity for quality testing environments
to support their development. In this paper, we introduce a Unity-based virtual
simulation environment for emerging mobility systems, called the Information
and Decision Science Lab's Scaled Smart Digital City (IDS 3D City), intended to
operate alongside its physical peer and its established control framework. By
utilizing the Robot Operation System, AirSim, and Unity, we constructed a
simulation environment capable of iteratively designing experiments
significantly faster than it is possible in a physical testbed. This
environment provides an intermediate step to validate the effectiveness of our
control algorithms prior to their implementation in the physical testbed. The
IDS 3D City also enables us to demonstrate that our control algorithms work
independently of the underlying vehicle dynamics, as the vehicle dynamics
introduced by AirSim operate at a different scale than our scaled smart city.
Finally, we demonstrate the behavior of our digital environment by performing
an experiment in both the virtual and physical environments and comparing their
outputs.
