The M1 Hwy is currently being impacted by a truck crash approximately 500m north of the Karuah Bridge, north of Newcastle.
A B-double truck rolled down an embankment and into a creek about 3am on Tuesday.
The B-double truck was allegedly overtaking another truck when the second vehicle began veering into the B-double and the driver was forced to take evasion action, NSW Police said.
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Two trailers attached to the B-double landed on the grass median strip as a result of the crash.
The 53-year-old man behind the wheel of the B-double was not injured.
He was breathalysed at the site of the crash and returned a negative result.
NSW Police are investigating the crash and urge anyone with relevant information, including dashcam video, to come forward.
Southbound traffic is being diverted through Karuah, with diversions expected to remain until Tuesday afternoon.
