Four dead in NSW road crashes

Four people have died within 24 hours following separate road crashes across NSW.

The first to die was a man in his 40s whose 4WD collided with a B-double truck on the Riverina Highway near Lowesdale about 7.45pm on Sunday.

Police say the man was the sole occupant of the 4WD, while the truck driver was treated for back pain before being taken to hospital by paramedics.

Six hours later another man died after he lost control of his car on the Hume Highway near Little Billabong about 130 kilometres from the first crash.

NSW police said the car rolled before coming to rest on an embankment on the opposite side of the road.

A passenger in the car was taken to Albury Hospital for treatment.

On Monday morning a 93-year-old woman died in hospital, nearly a week after her car collided with a truck on the Snowy Mountains Highway at Gilmore.

Later in the afternoon a 34-year-old man was killed in a head-on collision in the state's north.

Emergency services were called to Rous some 15km from Ballina about 3.50pm.

The 34-year-old male driver and sole occupant of the first vehicle died at the scene.

A woman and child from the second vehicle were conveyed to Lismore Hospital for precautionary checks.

Police are investigating and have called for witnesses.