Between 1991 and 2011, the population of Delhi and its adjoining cities more than doubled from approximately 10 million to 22 million while the number of registered cars and motorbikes increased from 1.6m in 1991 to around 8m today.
A new metro has made little impact, experts say, as most of its users previously travelled by buses, bicycles or on foot. Car users have remained reluctant to switch to public transport.