The A27 was closed in both directions at Selmeston near Polegate after a two car smash.
The emergency services received calls to the scene shortly before 4.20pm.
Police officers and firefighters closed the trunk road when they arrived.
One man was trapped in his car. He was released at 4.55pm.
The severity of his injuries remains unclear.
Officers began to reopen the road at about 6.20pm.
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