Currently most cars run of fossil fuels such as diesel and gasoline and produce 25% to 75% of the chemicals that pollute the air. Fossil fuels release hydrocarbons like carbon monoxide and carbon dioxide when they are combusted. "Carbon dioxide accounts for over 80% of the total greenhouse emissions in the United States."" (www.transportation.ani.gov) Hydrocarbons are causing the ozone to deplete and global warming, which could eventually lead to the devastation of our planet. We have to stop or reverse the damage done to our atmosphere in order to save our planet for future generations.
Fortunately the United States government recognizes the seriousness of greenhouse emissions and the impact on global warming and is making progress in reducing gas emissions from vehicles. Travel growth has risen faster than the improvement improvements in energy efficiency but this doesn't stop the United States government from promoting energy efficiency, use of renewable energy and trip reduction thru public and private programs. There has been significant development of fuel-efficient vehicles, researching options for cleaner fuel, programs implemented to reduce travel and even incentives for those people who modify or buy vehicles that can operate with a cleaner fuel source.
Because the government and society have increased pressure, automakers have been faced with the challenge to build more fuel-efficient cares. All new vehicles must meet federal emission standards but the older the vehicle the more pollution it produces. Automakers must conform to the laws and have responding by producing different vehicles like an electric and hybrid cars. The human perception of electric cars is that they are impractical because they cannot go far or fast enough to fulfill their everyday commuting needs. A hybrid car, on the other hand, is a vehicle that powered by two or more sources. But like most concept cars, it is the public they have to convince that owning one of these will be comparable to what they own today.