Two men have been arrest on suspicion of dangerous driving after a crash took place on the A23 at Pease Pottage on Saturday.
The incident took place around 7:30am, involving a Grey Mercedes and a private ambulance on the northbound carriage way.
Officer are also seeking dash cam and CCTV footage of the Mercedes. They are also looking for the driver of a tipper truck, carrying a crane attachment, which the ambulance was passing at the time of the collision, to come forward as a witness.
The 24-year-old and 29-year-old have been released on bail for further investigation.
Anyone with information is urged to contact Sussex Police.