The collision, involving a blue car and motorcycle, happened at about 4.50pm in Badminton Road, Yate on Monday, May 22.
The motorcyclist was taken to hospital with serious leg injuries.
His condition is not believed to be life-threatening.
A 39-year-old man, who was arrested, has since been released under investigation.
Anyone who can help their enquiries is asked to call 101, giving reference number 5223119312.