One dead, one critical after truck and van collide on M1 north of Sydney

A man has died in a crash involving a van and a truck on the M1 north of Sydney.

It's believed the van and truck collided while travelling northbound at Somersby, about 1km north of the Kariong turnoff.

The male driver of the van died at the scene. A male passenger is in a critical condition and has been transported to hospital.

The driver of the truck was not injured.

Police are investigating.