A man was airlifted to Canberra Hospital after a truck rolled on the Hume Highway near Yass on Thursday night.
NSW Police said emergency crews were called to the crash about 11.10pm. The southbound B-Double had landed on its side, blocking both lanes.
The truck driver, a 50-year-old man, was trapped for a short time before he was freed and taken to Canberra Hospital with multiple injuries.
He remained there in a serious condition as of 4am Friday.
While traffic had been diverted down Barton Highway and Yass Valley Way for much of the night, as of 6.45am a NSW Traffic spokeswoman said one northbound lane had reopened.
"There are some delays, because one trailer of the B-double still remains on the road, but traffic isn't looking too bad now," she said.