The idea of internal combustion engines (ICE) running on hydrogen, known as Hydrogen Internal Combustion Engines (H2ICE), presents an intriguing approach to green transportation without the emissions associated with traditional ICE vehicles. While electrification remains a primary method for decarbonizing transportation, the slow adoption of battery electric solutions has prompted a closer look at H2ICE technology. H2ICE vehicles offer a way to leverage mature ICE technology while eliminating carbon emissions by using pure hydrogen as fuel, resulting in a drastic reduction of CO2 emissions compared to conventional ICE vehicles. However, the transition to H2ICE vehicles is not without challenges. One significant issue is the formation of nitrous oxides (NOx) during hydrogen combustion, which requires careful management to ensure emissions reductions. IDTechEx's research delves into various engine parameters affecting NOx formation, including air-fuel ratio and engine speed, and explores methods like catalytic converters to mitigate NOx emissions. The color of hydrogen, indicating its production method, plays a crucial role in determining the overall lifecycle emissions of H2ICE vehicles. While green and yellow hydrogen offer minimal CO2 emissions, their limited availability and high costs pose obstacles to widespread adoption. The report highlights the importance of efficiently producing, storing, and utilizing hydrogen to optimize emissions reductions. In conclusion, the potential of H2ICE technology for green transportation is promising, provided that challenges such as NOx emissions and hydrogen production efficiency are effectively addressed. By combining the benefits of ICE familiarity with zero emissions, H2ICE vehicles could play a vital role in the transition to a more sustainable transportation sector.