Delhi is the second-largest metropolis in India. With over 17.3 million residents, it is the eighth largest metropolis in the world.
Buses are the most popular means of transport in the city, serving about 60% of the total demand. As of 2007, the Delhi Metro consists of three lines with a total length of 65 kilometers and 59 stations. Construction ongoing through 2020 will create a network longer than that of the London Underground.
Despite public transportation, motorization in Delhi is increasing at an alarming rate. The number of motor vehicles has increased from 540,000 in 1981 to 5.1 million by 2000. Delhi has more motor vehicles than Mumbai, Calcutta and Chennai combined. The result is extreme congestion on Delhi roads, an increase in road accidents, fuel wastage, and environmental pollution. Motorized vehicles alone contribute to about two-thirds of atmospheric pollution.