The 61-year-old van driver has died after he crossed the central reservation of a dual carriageway near Poole and crashed into a tree.
The man, from Christchurch, suffered serious injuries and died at the scene. His passenger suffered a serious head injury and was taken to Poole Hospital.
Parts of Waterloo Road were closed after the crash at 14:00 GMT on Friday.
The section between Cabot Lane and Darbys Corner roundabout closed for five hours for a police investigation.
Sgt Mark Scammell, of the traffic unit, said: "Sadly the driver was pronounced dead at the scene and his family are being supported by specially trained officers."