The health benefits of cycling daily rather than taking a car for short trips outweigh the risks of inhalation of air pollutants. Daily exercise prolongs life expectancy by approximately 3.4 years whereas inhalation of polluted air reduces life expectancy by 1 to 40 days. Regular cycling boosts physical fitness and is an efficient way to prevent obesity.Switching from a car to a bicycle saves 150 g of CO2 per kilometre. Each 7 km by bicycle will save an emission of 1 kilogram of CO2 as compared to the same distance covered by car. In a five-year period, Dutch people avoided 1.41 million tonnes of CO2 each year through cycling. This saving is equivalent to 54.4 million trees being planted each year. The climate value of cycling in the wards of Stone Town, Zanzibar was estimated to be 1,062.4 tonnes of CO2 per year, which corresponds to US$20,994, if it were traded on the carbon markets. An amount approximately equivalent to 10 times the average income in the country. So it's the cheapest mode of transport and good exercise also.