Areas with no source of electricity remain in darkness until the comes up, because street lights need a power supply. British firms offer new appliances, such as solar-powered street lights. They work by using energy accumulated during the day from a solar panel. The batteries are being charged during the day and then it's power is used for lighting. The system can be used for one individual light or a number of them. In the south of Saudi Arabia a motorway tunnel miles from any power supply is lit day and night by solar-powered devices. The advantages of sun-powered lamps are that they can bring light to areas distant from any other power supply and that they do not pollute the environment.