A pedestrian has died in Palmerston North after being hit by a car, while a person has also died in a separate car crash on the South Island's West Coast.

The man in Palmerston North was hit around midnight when a vehicle driving on Main St in the suburb of Roslyn clipped another vehicle, hit a traffic island and rolled onto the footpath, police said.

An ambulance was called but the pedestrian died at the scene.

A passenger in the vehicle was also seriously injured, and the driver and front passenger received minor to moderate injuries, police said.

"The Serious Crash Unit has been advised and the circumstances of the crash remain under investigation," police said.

The West Coast fatal crash took place in Charleston in the Buller District just after 4.30am today.

Emergency services rushed to the crash on State Highway 6, near Croninville Terrace, but the sole occupant of the car died at the scene, police said.

One lane is open on SH6, and the crash remains under investigation, police said.