Well, the thing is that, the congestion charges, they were introduced first as a trial, so they were introduced in January and then abolished again at the end of July, followed by a referendum, and then they were reintroduced again in 2007, which of course was a wonderful scientific opportunity.
Bueno, la razón es que, los cargos por congestión se introdujeron inicialmente de modo experimental, por lo que aparecieron en enero y se quitaron a finales de julio, seguidos de un referéndum, y luego fueron reintroducidos otra vez en 2007, lo que por supuesto fue una maravillosa oportunidad científica.