As one of the most important enablers of Intelligent Transportation System (ITS), Inter-Vehicle Communication (IVC) have been a hot research direction in nearly a decade. To improve vehicle safety and cooperative systems, most of ITS applications need efficient and stable Vehicular Ad hoc Networks (VANETs) among vehicles and infrastructures, which can be set up by Geocast routing protocols. Some of these applications require the protocols, known as region-based Geocast routing protocols, supporting to broadcast messages to vehicles within a specific geographic region. Since different protocols are appropriate for different purposes or occasions, it is significant to simulate protocols and evaluate their performances under a variety of scenarios. Therefore, this paper focuses on investigations of simulation environment configurations for some known Geocast routing protocols. According to the investigations, a region based Geocast routing simulator is designed and developed. To demonstrate the effectiveness and the reliability of this simulator, several protocols are simulated and the performances of them are presented. © 2014 IEEE