The government has approved phase III of National Highway Development Programme (NHDP), which includes four-laning of 10,000 km of NHs on build, operate and transfer (BOT) basis. The upgradation would include corridors having high-density traffic, connecting of state capitals with Golden Quadrilateral and North South-East West corridors, and tourism centres and places of economic significance, Union minister for shipping, road transport and highways TR Baalu told a press conference on Thursday. He said phase III has been approved in two phases. Phase III (A) is for implementation of widening and strengthening of 4,000 km, while under phase III (B) a project report for 6,000 km will be prepared.