How did London's congestion pricing succeed?

London's mayor, Ken Livingstone, explains:

This success had preconditions. In London, as will be the case in New York or any other city, an enhanced public transportation system was critical. To ensure readiness, we made significant upgrades to public transport. Our investment focused on enhancing London’s bus system, rather than the subway, because we needed to increase capacity in the quickest, most cost-effective way.

Specifications for a modern, more comfortable fleet were introduced, bus lanes were added, and more inspectors were put on to ensure buses ran at regular intervals. With London’s buses a more attractive alternative, the number of bus trips a day has risen to six million, an increase of two million from 2000 — with ridership growing most rapidly among the highest-paid social groups. In turn, this helped relieve pressure on the subway, ensuring it continued to run smoothly. Investment in public transport continues to this day, aided by the revenue from the congestion charge — the equivalent of some $200 million annually.