function fully or partly on alternative energy sources other than fossil fuel or less carbon-intensive than gasoline or diesel. Another option is the use of alternative fuel composition in conventional fossil fuel-based vehicles, making them function partially on renewable energy sources. Other approaches include personal rapid transit, a public transportation concept that offers automated, on-demand, non-stop transportation on a network of specially built guideways. Electric and fuel cell-powered Examples of vehicles with reduced petroleum consumption include electric cars, plug-in hybrids and fuel cell-powered hydrogen cars. Electric cars are typically more efficient than fuel cell-powered vehicles on a Tank-to-wheel basis. They have better fuel economy than conventional internal combustion engine vehicles but are hampered by range or maximum distance attainable before discharging the battery. The electric car batteries are their main cost. They provide a 0% to 99.9% reduction in CO2 emissions compared to an ICE (gasoline, diesel) vehicle, depending on the source of electricity. Hybrid electric vehicles Hybrid cars may be partly fossil fuel (or biofuel) powered and partly electric or hydrogen-powered. Most combine an internal combustion engine with an electric engine, though other variations too exist. The internal combustion engine is often either a gasoline or Diesel engine (in rare cases a Stirling engine may even be used). They are more expensive to purchase but cost redemption is achieved in a period of about 5 years due to better fuel economy. Compressed air cars, stirling vehicles, and others Compressed air cars, stirrling-powered vehicles, and Liquid nitrogen vehicles are less polluting than an electrical vehicles, since the vehicle and its components are environment friendly. However, compressed air vehicles are far beneficial to the environment than vehicles that are considered "eco-friendly". Take the Toyota Prius, although it is marketed as an eco-friendly vehicle, it has an environmentally harmful production process. In the words of Jeremy Clarkson, a renown British car show host and expert, "The recent study found that in the long term it does more environmental damage than a Land Rover Discovery". Alternatively, compressed air vehicles are less environmentally harmful due to their air engine, which allows the car to run on compressed air instead of fuel. The engine is pumped by air instead of gasoline explosions, thus having zero emission motors, no pollution or oil. Solar car races are held on a regular basis in order to promote green vehicles and other "green technology". These sleek driver-only vehicles can