Emergency services were called to Bath Road, Cheltenham, at around 5.30pm on Thursday 6 August following a report of a collision involving a cyclist and a caravan being towed by a car.
The incident happened near the junction with Kew Place. According to information attributed to Gloucestershire Police, the driver of the car did not stop and had left the scene before officers arrived.
The cyclist was taken to Gloucestershire Royal Hospital for treatment for serious injuries and was reported to remain in hospital.
Police said officers were continuing to investigate the collision and CCTV enquiries were taking place.
Investigators have appealed for anyone who witnessed the incident, or who has relevant CCTV or dashcam footage, to contact Gloucestershire Police and quote incident 53260067937.
How to contact police
Information can be provided through Gloucestershire Police's official existing-case reporting service. Anyone contacting police about this incident should quote incident 53260067937.