Vehicular Ad-hoc Network (VANET) is one of potential candidate to application of Intelligent Transport System in a city. This VANET technology allows any vehicle using this modem may be functioned as a repeater for other VANET members. In order to support emergency response to the public health facilities, use of VANET technology in the medical vehicles will improve punctual response in responding accidents or event natural disasters. This paper proposes a model and an application using clustering method for maintaining optimum and reliable communication among medical vehicles. This model applies in the urban environment (part of Surabaya City). Main tools are including the SUMO and the OMNet++ simulators are applied to simulate the scenario of the medical vehicle operation. The simulation combines the capability of SUMO in providing map of operation environment, delivery performance, routing algorithm of data transmission. Evaluation of the VANET communication performance is then applied to the packet delivery ratio (PDR), end-To-end delay and routing overhead. The simulation results show that the PDR, delay and the overhead is correlate linearly to the number of vehicles.