The standard charge is £11.50 for each day, for each non-exempt vehicle that travels within the zone, with a penalty of between £65 and £195 levied for non-payment. Enforcement is primarily based on automatic number plate recognition (ANPR). Transport for London (TfL) is responsible for the charge which has been operated by IBM since 1 November 2009. During the first ten years since the introduction of the scheme, gross revenue reached about £2.6 billion through December 2013. From 2003 to 2013, about £1.2 billion (46%) of net revenue has been invested in public transport, road and bridge improvement and walking and cycling schemes. Of these, a total of £960 million was invested on improvements to the bus network.