Original sentence: According to TfL the objective of the increase is to recoup inflation over the previous three years and ensure the charge remains an effective deterrent to making unnecessary journeys in central London.There has been criticism because during the first ten years since the scheme was implemented, gross revenue reached about  billion, but only  billion has been invested, meaning that 54% of gross revenues have been spent in operating the system and administrative expenses
Edited sentence: According to TfL the objective of the increase is to recoup inflation over the past three years and ensure the charge remains an effective deterrent to making unnecessary journeys in central London