Two men fled after the car they were in struck an 86-year-old woman and left her with severe injuries.
She was hit by a Peugeot 405 travelling south near the railway level crossing in South Farm Road.
Police said there were three men in their mid to late 20s in the Peugeot but two fled the scene after the accident at 12.30pm yesterday.
The other is helping police with their inquiries.
The injured pedestrian was taken to Worthing Hospital.
Witness Paul Bristow, from Worthing, said: "I was walking up the road and these lads were coming through in the Peugeot and the gates on the level crossing were coming down.
"They hit a verge and then hit an elderly woman. She went up about 10ft in the air. It made my stomach churn.
"A man shouted at the car to stop, I don't know if they realised they had hit someone."
The man helping with police inquiries has been released on bail. He is a 27-year-old from Bournemouth and will return to Worthing police station on March 22.
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