The intense smog experienced in Paris last week led to authorities banning certain number plates on alternate days. But does the tactic actually work?

There are a number of traffic restrictions based on licence-plates currently operating around the world, usually involving cars with plates ending in odd numbers being permitted on the roads one day, then those with even numbers being permitted the next.

Beijing, Mexico City and Athens are some of the global cities that have implemented such bans. But according to the website Low Emission Zones in Europe, people have been buying cheap, high emissions vehicles bearing opposing number plates to complement their main car – meaning they can drive on any day. Aside from rendering the plate bans much less effective, it also means more cars are put on the road.

And in such number plate ban schemes, there are no incentives for greener cars; they get penalised along with more polluting vehicles.

Some experts point to low-emissions zones (LEZs), which ban polluting cars from certain areas. The first was implemented in Stockholm in 1996, with many more having sprung up across Europe.

Congestion charges, such as those issued in central London, have also had a big impact on cutting the number of vehicles on the road, so therefore pollution.

The combination of LEZs and congestion charges cuts the numbers of vehicles on the road, ensuring that any remaining cars are greener.