Police remain at the scene of a fatal crash north of Mudgee which has blocked the Castlereagh Highway.
The highway is now closed between Lower Piambong Road and Tuckermans Road, with detours in place.
Emergency services were called to the scene 10 kilometres north of Mudgee at about 12.15pm on Thursday after two vehicles collided.
A woman died at the scene, while a second driver was trapped for sometime. A rescue helicopter has been called to assist.
The highway is expected to be closed for some time as inquiries continue, with crash investigators en route to the scene.
Southbound traffic is being diverted via Lesters Lane; northbound traffic is being diverted via Hill End Road.