Put quite simply, an alternative-fueled car is one that runs on non-traditional gasoline or diesel. In other words, it is powered by something other than just petroleum, which would include the standard plug-in electric cars, gas-electric hybrids or those which are solar powered. Now the compressed-air-powered piston engine cars with zero admissions are gaining mainstream attention as refill stations will soon be widely available in California. There is also hydrogen, liquid nitrogen, CNG Natural Gas, biofuels, steam and pedal-assisted hybrids. Whether any of these are viable for popular usage remains to be seen and is dependant on several factors and scenarios.