Sussex Police were called to the scene of the accident involving a motorbike on the A22, Hailsham Road shortly after 5am on Saturday 15th June.
The motorcyclist, a 34-year-old from Eastbourne, was pronounced dead at the scene.
A spokesman for Sussex Police said: “The road remained closed in both directions for investigation and recovery until late afternoon and we continue to establish the full circumstances of the incident, which is believed to have happened in the early hours of the morning.
“If you have any information, witnessed the incident, or have dashcam footage, you are asked to contact Sussex Police by emailing collision.appeal@sussex.police.uk, or by calling 101, quoting Operation Lewes.”