Edwin Van der Sar was following in his Bentley, but the Dutch keeper was not involved in the crash.
It was really "fortunate" that Ronaldo was not injured, said pc Nigel Snell.
The footballer's red Ferrari was badly damaged in the crash, with the front edge of the vehicle completely demolished. One of the wheels came off, ending up about 200 yards behind where the vehicle came to rest.
Manchester United confirmed that Ronaldo was not hurt. A club spokesman said: "He was involved in an accident this morning. No others car were involved."
"He's fine and is training as normal with the team this morning."
The Portuguese winger, who played on Wednesday night for United, has started on the bench against Derby County.
Ronaldo is due to play for United against Chelsea FC on Sunday.
Source: BBC News.
Thanks for reading!