London is one of the most congested, and polluted cities in Europe.
Londoners were introduced to a congestion charge in 2003, forcing motorists to pay extra when they enter central London.
The move had some impact on traffic levels, but in July 2010, authorities introduced a new scheme, in an effort to get more people out of their cars.
Al Jazeera's Barnaby Phillips reports from London.
Source: Al Jazeera