The collision occurred in the village of Barna, Co Galway, at about 5.40am. There was no other vehicle involved.
The driver, in his mid 60s, died at the scene.
His body was taken to University College Hospital Galway for a post-mortem examination.
The road was closed for a time to allow a collision investigation by Garda forensic experts.
Investigating gardai at Salthill have appealed for witnesses.
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