Abstract:Vehicular Ad-hoc Network (VANET) simulators have gained widespread adoption in the research community given the fact that they can simulate near real life scenarios to evaluate driver-safety applications without endangering human lives. In this paper, we present the VEhicular NeTwork Open Simulator (VENTOS), a closed-loop VANET simulator that combines the capabilities of both communication network (OMNET++) and vehicular traffic simulators (SUMO). As an alternative to current proprietary VANET simulators, VENTOS is a free, open-source simulator that is designed for vehicular traffic flow analysis and can incorporate new control logic, such as intelligent traffic controller, collaborative driving, dynamic routing, and self-driving capability. VENTOS supports V2X (Vehicle-to-Vehicle or Vehicle-to-Infrastructure) communication through dedicated short-range communication (DSRC) integration. This paper will give an overview of the VENTOS architecture and its extension, VENTOS-HIL, which supports hardware-in-the-loop emulation using physical devices such as On-Board Units (OBUs) or Roadside Units (RSUs). We then demonstrate how VENTOS can be utilized to simulate and evaluate the performance of multi-modal, adaptive traffic signal control (TSC) as well as to illustrate the security vulnerability of intelligent TSC in the presence of falsified data attacks.