Five cities that have implemented the odd-even car rationing scheme

Once known as the most polluted city in the world, Beijing took to rationing of vehicles in 2008. Odd-even was implemented on private vehicles again in 2015 and 2016. The city enforced an automated system to monitor traffic and violators, thus minimising scope of evasion or corruption. A fine of 200 Yuan (Rs. 2,000) was imposed on violators. With nearly 45 per cent of 3.3 million cars off the streets, vehicle emissions had reduced by 40 per cent according to a government study. The government has currently banned nearly a fifth of the private vehicles from operating in Beijing. Within three years, the city has built an extensive subway and public bus network. The subway is likely to cross the 600-kilometer stretch which is double the length of Delhi's metro system.

Paris, with a 2.24 million population had taken to the odd-even scheme in 2014. Cars with odd number plates were allowed on the roads on alternate days. Private vehicles with even number plates were banned from entering the city from 5.30 am until midnight. Electric, hybrid, or cars powered with natural gas and carpools with three or more passengers were exempted from the rule. Public transport was made free for that day. Two-wheelers, however, weren't exempted. This experiment was carried out only for a day till the time the desired air quality levels were achieved. Airparif, the city's air quality monitoring body, reported a reduction in traffic by 18 per cent and therefore a reduction in PM10 levels by 2 per cent. During rush hour, pollution fell by 20 per cent and nitrogen oxides fell by as much as 30 per cent alongside major roads.

Hoy No Circula which translates to 'today it doesn't circulate' was introduced as early as 1989 in Mexico. Depending on the last number of the registration plate, nearly 2.3 million vehicles were banned for one day per week. Similar to China's odd-even policy, cars with number plates ending with numbers 5 and 6 were prohibited on Mondays, 7 and 8 on Tuesdays, and so on. The rule was imposed between 5 am and 10 pm on all days except on weekends. A fine of $23 - $69 (Rs.1495 - 4485) was levied on violators. As per the city's air pollution monitoring stations, 11 per cent drop in carbon monoxide (CO) levels were recorded. However, this was met by a counter-productive move by residents of Mexico, as they started buying two cars with odd and even numbers. This saw an increase in CO levels of 13 per cent.

Vehicles in these two cities of Italy were restricted in December 2015 due to increase in smog. While in Milan, private cars and two-wheelers were banned for six hours a day for three consecutive days, Rome banned odd-numbered plates for nine hours on a Monday and even-numbered plates on a Tuesday. Also, as an alternative, both cities encouraged commuters to use public transport by issuing a single ticket for bus and metro that would be valid for the whole day.

Inspired by Mexico, Bogota, the capital of Columbia, also imposed the odd-even scheme during peak hours, for two days per week and also fined violators 15% of their daily minimum wages. Introduced in 1998, the scheme restricts four numbers every day for private vehicles. For example in 2011, on Mondays, number plates ending with 5, 6, 7 and 8 were banned and plates ending with 9, 0, 1 and 2 were restricted on Tuesday. To ensure that people did not follow Mexico and buy two cars, the authorities switch the combination of days and numbers every year since 1998.