Riten, I think the construction was completed sometime in the late 90's (including the Karnali Bridge). I think Nepali Man6e is quite right about its length.

If I can recall correctly: Kankerbhitta-Dhalkebar 256 km, Pathlaiya 109 km, Hetauda 28 km, Narayanghat 78 km, Butwal 115 km, Kohalpur 236, Banbaasa 204

Total: 1026 km (shortest so far )