There are two broad approaches to achieve environmental controls: regulation (command, the ‘stick’, or punishment) and incentives (reward, or ‘carrot’). Strict adherence to ‘the polluter pays principle’ means less support for incentives and more of a command approach. Examples of green incentives include reduced landing fees for less noisy aircraft, cheaper unleaded petrol to discourage use of fuel with additives and subsidies for alcohol-fuelled cars.