An international standardization of data communication is necessary at both the train and vehicle levels. Trains with varying composition during daily service-such as metros, or suburban and international trains, need a standard form of data communication for train control, diagnostics, and passenger information. Such communication should configure itself when vehicles are coupled on the track. At the vehicle level, a standard attachment of equipment would serve manufacturers, suppliers, and operators. Manufacturers could assemble pretested units, such as doors manufactured by subcontractors, which include their own computers. This paper presents a train communication network simulator (TCNS) that can be used to evaluate the performance of TCN. TCN was accepted as the standard of the protocol for the communication network in trains. We carry out some simulation tests using the TCNS to show practical uses of the simulator. Results of some simulation tests are also reported