PC Tom Van Der Wee said officers are currently making enquiries to locate a driver who 'crashed on the A27 and ran off' shortly after 9pm.
In a tweet whilst the incident was ongoing, he added: "We’re on scene at a road traffic collision on the A27 Emsworth with Sussex Roads Policing Unit, South Central Ambulance Service and Hampshire Fire and Rescue Service.
"Lane 1 on the westbound carriageway is closed whilst we deal with the incident."
The police officer said the vehicle had collided with the central reservation before ending up in a bush, but there were no known injuries.
He added: "It was later confirmed that the driver had been witnessed running from the scene prior to the arrival of the emergency services."
The road was cleared shortly after 11pm and PC Van Der Wee asked anyone who witnessed the incident, or who has any information which may assist the investigation, to call Sussex Police quoting CAD 1096 17/02/19.
Fellow police officer Pete May also tweeted about the incident. He wrote: "If the driver would like to attend custody for a breath test I'd be most grateful."