Paris Cars with even number plates were banned from entering the city between 5:30 am until midnight to control the air pollution attributed to vehicle emissions. The decision was taken by the city government. Before the rule was imposed, the government also reduced speed limits around Paris by 20 km per hour and provided all public transportation for free to encourage one and all to use it. Violators would be fined 22 euros. The rule was the huge success there.In Mexico The rule known as the Hoy No Circula was introduced as early as 1989. Since they didn't have even half as many cars back then as Delhi has currently, they didn't have to do it the odd-even way. They would pick out numbers. For example, Sundays, number plates ending with three and four were banned, Mondays five six, Tuesdays seven eight, so on and so forth. Violators were asked to pay anywhere between $23 to $69. The response was great as pollution was reduced by as 11%.Bogota The Columbian capital of Bogota also implemented the rule of Pico y Placa ('peak and plate'). They just started banning cars during the peak hours for two days a week. They wanted their citizens to take them seriously so they started fining the violators 15% of their daily minimum wages. To make sure people don't try to act like they did in Mexico and just buy two cars, they started changing the combination of days and numbers around every now and then.Beijing In an attempt to improve the air quality of Beijing, China, before the 2008 summer Olympics implemented a temporary road space rationing. They imposed restrictions on private vehicles by allowing even and odd license plates to drive on alternate days with the violators having to cough up 200 yuan for breaking the rules. As reported their daily reduction of vehicle emissions of up to a staggering 40%!