Cars are wonderful inventions and even if you or your family don't own a car it is impossible to imagine life in a city today without one. Already, there are about 523 million cars on the roads worldwide. In developing countries, there are three motor vehicles for every 100 people, but in richer industrialised countries there are 50 motor vehicles for every 100 people.

Yet globally, car accidents kill over 3,000 people every single day . Road traffic injuries are the ninth leading cause of all deaths. And car accidents injure or disable as many as 50 million more every year. Nearly 85% of these accidents occur in low and middle-income countries such as India , Pakistan , Africa and Sri Lanka . Unlike in rich countries, where those getting hurt or killed are the drivers and passengers of cars, the people who are most at risk of being involved in a road accident in India are pedestrians, cyclists, motorcyclists and others. In New Delhi , 75% of people killed on the road are pedestrians, cyclists and motorcyclists, while only 5% of those killed are drivers or car passengers.

Apart from killing people directly in accidents, cars also have a huge environmental impact. This stems from two sources: 1) all the elements that go into the making of a car from the iron, silica and bauxite mines that scar the earth, and the factories making the cars that spew out pollution, and 2) the problem of what to do with cars when they are too old to use. Perhaps the steel can be used to make new cars. But what about the glass, plastics, rubber tyres and electronic parts?

What is more worrying, however, is not so much the car but the power that drives it, the internal combustion engine. This machine has possibly changed the world more than any other invention (except perhaps the plough). Cars, buses, trucks, tractors, trains, planes and ships are now mostly powered by versions of this engine, which works by producing mechanical movement by the energy of exploding petrochemicals. These carry us, our food, our building materials, our medicines, and without them modern farming would not be possible. But, while this engine does so much for us it also pumps its exhaust out into the air. From the burning of fuels like petrol or diesel, millions of tonnes of exhaust are sprayed into the air every day containing poisonous gasses such as oxides of sulphur, carbon monoxide, nitrogen oxides to name only a few. Plus tiny solid particulate matter called dioxins. These cause chronic respiratory illness, asthma, lung cancer, and contribute to cardiovascular diseases. In the US alone, 30,000 people die every year from respiratory illnesses related to car exhaust, while another 12,000 people die prematurely because of such exhaust.

Some of these exhaust gases are also greenhouse gases and are a major case of global warming, contributing up to a quarter of all greenhouse gases created.