Transmissibility measurement and analysis have attracted attention from the automobile industry for years, but an objective test procedure is yet to be established. The paper proposes a method of using a newly-designed mass dummy for benchmarking measurement, as the first step towards the goal of establishing a metric of human occupant vibration comfort. Two seats are tested and the results are presented. Discussions are directed toward interpreting the data measured from a rigid mass, instead of a human seat occupant. The capability of distinguishing the transmissibility differences between seats shows the possibility of using a rigid mass dummy to assess the seat vibration comfort quality. Further work needs to be done to correlate the dummy measurement data to human occupant measurement data and to establish the seat vibration comfort metric based on the correlation. This paper is the first of a series of publications on vibration comfort development at Lear Seating Corporation.