as scheduled), and was more than a year behind on the refurbishment of 78 District line trains. It was also behind on its track replacement programme, having completed 28 km instead of the scheduled 48 km. In March 2005, the House of Commons Transport Select Committee noted that "Availability is the most important factor for Tube travellers. All the infracos needed to do to meet their availability benchmarks was to perform only a little worse than in the past. On most lines, they did not even manage that." Metronet was also declared at fault by an accident investigators' report into a May 2004 derailment at White City, for failing to implement sufficient safety checks despite being ordered to do so by TfL. TfL takes over infracos Metronet, using its shareholders as its main contractors, was unable to meet its targets and track replacement and station refurbishments fell behind schedule. With increased costs it went into administration in 2007 and TfL took over responsibilities. The UK government tried to find another private firm to fill the vacuum left by the liquidation of Metronet. However, only TfL expressed a viable interest in taking over Metronet's responsibilities. The case for PPP was also weakened in 2008 when it was revealed that the demise of Metronet had cost the UK government £2bn. The five private companies that made up the Metronet alliance had to pay £70m each towards paying off the debts acquired by the consortium. But due to a deal struck with the government in 2003, when the PPP scheme began operating, the companies were protected from any further liability. The UK taxpayer therefore had to foot the rest of the bill. This undermined the argument that PPP would place the risks involved in running the network into the hands of the private sector. By 2010, Tube Lines was behind schedule on the Jubilee line upgrade and after conflict arose over costs of future work in that year's PPP review, TfL bought Tube Lines for £310m ($458m). Despite the collapse of the PPP, substantial investment to upgrade and modernise the Tube has taken place - with new trains (such as London Underground S7 and S8 Stock), new signalling, upgraded stations (such as King's Cross St Pancras) and improved accessibility (such as at Green Park). Recent history The Oyster card, a stored-value contactless smart card that can be used on Transport for London services