The literature on the modeling of diffusion of technologies typically uses historical data to calibrate a model. For cases where data on the diffusion of comparable technologies are not available and where high multi-sector stakes are involved, models that use more specific information may be useful. The potential transition to alternative transportation vehicle technologies and fuels, like fuel-cell vehicles and hydrogen, would be an example of such cases. We propose an integration of theoretical frameworks on the diffusion of innovations with data on stakeholders' opinions, to develop estimates of FCVs' market-share evolution. Our estimates of the time scales required for the market, particularly for the initial stages, are longer than those obtained in other studies.