With the depletion of fossil fuel resources and the potential consequences of climate change due to fossil fuel use, much effort has been put into the search for alternative fuels for transportation. Although there are several potential alternative fuels, which have low impact on the environment, none of these fuels have the ability to be used as the sole "fuel of the future". one fuel which is likely to become a part of the over all solution to the transportation fuel dilemma is hydrogen. in this paper, The Toyota Corolla four cylinder, 1.81 engine running on petrol is systematically converted to run on hydrogen. Several ancillary instruments for measuring various engine operating parameters and emissions are fitted to appraise the performance of the hydrogen car. The effect of hydrogen as a fuel compares with gasoline on engine operating parameters and effect of engine operating parameters on emission characteristics is discussed. Based on the experimental setup, a suite of neural network models were tested to accurately predict the effect of major engine operating conditions on the hydrogen car emissions. Predictions were found to be +/- 4% to the experimental values. This work provided better understanding of the effect of engine process parameters on emissions. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.