At 11.40pm on Wednesday 10 February, a black Volkswagen Golf was travelling east towards Chichester on the A27 when it crashed.
The driver – a 25-year-old man from Havant – was sadly pronounced dead at scene.
The passenger – a 19-year-old man from Havant – suffered life-threatening injuries and has been taken to hospital for treatment.
The road is likely to be closed in both directions between Fishbourne and Emsworth roundabouts for some time whilst the investigation takes place, and motorists are advised to seek alternative routes.
Police are appealing for witnesses and are particularly interested to hear from anyone with dash cam footage of the collision or the Golf being driven prior to the collision.
Police would also like to hear from the driver of a Red Audi A3 who may be able to assist with the investigation.
Please call 101 or email firstname.lastname@example.org quoting Operation Westdown.