Unlike many of the hybrid and "green" vehicles currently available on the market, hydrogen cars offer the promise of zero emission technology, where the only byproduct from the cars is water vapor. Current fossil-fuel burning vehicles emit all sorts of pollutants such as carbon dioxide, carbon monoxide, nitrous oxide, ozone and microscopic particulate matter. Hybrids and other green cars address these issues to a large extent but only hydrogen cars hold the promise of zero emission of pollutants.
All types of vehicles can run on hydrogen, which is available in a variety of forms. Combustion works the same way as traditional vehicles fueled by gasoline. Hydrogen is burned in the engine to fuel the vehicle. The hydrogen gases and water molecules are separated. The hydrogen gas is forced into the combustion chamber and burned to create energy.
There are more hydrogen fuel cell cars being built currently than any other kind. Let's also not forget about hydrogen-on-demand vehicles that are either using a hydrogen compound or electrolyzing water to create hydrogen, avoiding the compressed or liquid hydrogen refueling scenario altogether.
Many companies are currently researching the feasibility of building hydrogen cars, and most of the automobile manufacturers had begun developing hydrogen cars. But most hydrogen cars are currently only available in demonstration models or in a lease construction in limited numbers and are not yet ready for general public use.