Police Scotland launched a search for Iain MacDonald, 58, after he was reported missing from the Daliburgh area of South Uist at about 4.30pm on Sunday.
Officers are keen to check if Mr MacDonald is “safe and well” following the one-vehicle collision.
He is described as 5ft 9ins tall, of medium build with white short hair and facial hair.
When last seen, he was wearing a green body warmer, a red checked shirt, black trousers and dark-coloured boots.
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Sergeant Fiona Murray said: “We are appealing to anyone who has seen Iain, or has any information regarding where he may be, to come forward and speak to officers.
“We understand Iain was the passenger of a car that was involved in a one-vehicle crash prior to going missing, so we are keen to trace him to ensure he is safe and well.”
