Authorities in India's capital Delhi have launched major restrictions on private cars to curb alarming levels of pollution.
Private cars with even and odd number plates are being allowed on alternate days from January 1 in an initial two-week trial.
Taxis and emergency vehicles like ambulances, police cars, fire engines have been exempted from the order.
Delhi has experienced hazardous levels of pollution this winter.
The local government announced the scheme after a court ordered authorities to tackle pollution levels more than 10 times the World Health Organisation's safe limits.
The government has made several exemptions to make it easier for people to follow the restrictions. The plan will be imposed between 8am and 8pm from Monday to Saturday.
Women will be allowed to drive their cars on all days but they can only be accompanied by women, and children below the age of 12. Cars carrying disabled people will also be allowed on all days.
Along with two wheelers, cars operating on natural gas have been exempted. In cases of medical emergency, people will not be stopped from taking patients to hospitals.
The government has hired around 3000 private buses to provide shuttle services into the city from residential areas to ease the extra pressure on the public transport network.
Schools have also been shut until the trial ends on 15 January so that their buses can be used as public transport.
The government has launched an app that people can use to book tuk-tuks to improve last-mile connectivity from the Metro stations.
Traffic policemen and several thousand volunteers will check cars at intersections and violators will be fined 2000 rupees ($NZ44) and asked to return.
"The biggest challenge is to make people realise that this fight against pollution is for them, for their health, for their own good," Delhi Transport Minister Gopal Rai told AFP news agency.
Critics, however, say the plan is not practical - they say that in a city with an inadequate public transport system and poor last-mile connectivity, the new measures are likely to inconvenience commuters.
"Let's not convince ourselves wrongly that a simple odd-even policy will solve the overall air pollution issue," AFP quoted Arunabha Ghosh, head of the Delhi-based Council on Energy, Environment and Water, as saying.
"Otherwise, we will be simply kicking the can down the road and we will create a feeling of distrust among citizens and the government machinery."
Delhi resident Pankaj Mehta, who drives 45km to work daily, told AFP that the restrictions would make commuting difficult.
"Rickshaw, then metro, then feeder bus, then walk - back and forth. A travel nightmare," he said.
"But if it makes breathing easier, then it may be worth it."
Environmental activists have welcomed the decision, saying the situation is so grim that urgent drastic steps are needed.
New car sales are soaring in India, with 1400 extra cars taking to the capital's streets every day.