I have always paid attention to green products that conserve energy,  such as electric cars,  which have been in development for a long time.   It looks like they are widely available to the public and many car companies have created their own models.   Besides the batteries being charged more quickly,  they can also reach faster speeds.   One of the interesting things about the car is the sound.   Electric cars are naturally very quiet,  but in order to alert pedestrians when an electric car is approaching,  a sound that mimics that of a regular car engine,  has been added.   Although I am very curious as to what it will be like one day when there is no sound of cars on the street,  safety is always more important.