George Clooney waited for the "switch to turn off" when his head smashed into the windshield of a car during that motorbike accident last year in Italy ... and says he knew instantly he had to quit riding.
George described the horrific accident to The Hollywood Reporter, saying he was doing 70 MPH when he smashed into a Mercedes-Benz sedan. He immediately noticed his helmet had split and assumed he'd suffered a fatal neck injury.
Considering how nasty it looked on video... George is right. Good call to hang up the riding gloves and helmet. He describes it in the vid, starting at 31:35.
As we reported ... George was tossed about 20 feet in the air on the island of Sardinia when his scooter was cut off by the Mercedes.
Pretty miraculously, he was back on set just 4 days later in Sardinia to shoot his Hulu series, "Catch 22." Chauffeur-driven, we're guessing.