The on board multiplexing communication system is regarded as a necessary technology for the future of electronics in automobiles. Many companies are developing multiplexing systems, and the ISO and SAE have been active in establishing standards for communication protocols. The proposed communication protocols have different specifications. Consequently, no compatible evaluation standards exist, so it was difficult to compare one protocol to another.Therefore, to assist the standardization activities of the ISO and SAE, we have developed an evaluation method for distributed multiplexed communication systems and have evaluated each of the proposed protocols using this method. These evaluations were performed from the point of view of the future users of these systems.In this paper we present the results of the experiments on eight distributed multiplexed communication systems, each of which consists of a communication IC and the proposed physical layer. These evaluations were performed by the fourteen corporate members of the JSAE serial data communication evaluation subcommittee.