Police are appealing for witnesses following a serious collision near Stow-on-the-Wold.
The crash happened on the A429 Fosseway on Saturday 25 April and involved a motorbike and a car.
A man in his 20s riding a Triumph Trident was seriously injured and taken to University Hospital Coventry.
Officers believe a dark-coloured Volkswagen Sharan may have been directly behind and could have seen what happened.
Anyone with information or footage is being urged to contact Gloucestershire Police.