A total length of 16,798.61 kilometres of national highways is under the public-private partnership (PPP) arrangement and 331 fee plazas are operational as of now, Parliament was informed on Thursday. In a written reply to a query to the Lok Sabha, Minister of Road Transport and Highways Nitin Gadkari said Rs 28,499.12 crore was collected by fee plazas on national highways in 2021-22.