Cars which use less environmentally damaging fuel sources than petrol would be good for the protection of the environment. Petrol and diesel engines produce pollution both on a local and a global scale, contributing to poor health and global warming. They are also a major consumer of non-renewable energy, depleting global reserves and making us dependent upon oil-rich states for our energy security. Therefore, a scheme which can encourage people to use alternative fuels instead of petrol will have a positive environmental, economic and political impact.