POLICE are appealing for witnesses of a collision in Aust today after a cyclist suffered life-threatening injuries.

The incident, which involved a car and a cyclist on the roundabout of the A403, near junction one of the M48, took place just after 10am.

The cyclist suffered significant head injuries, and was rushed to Southmead Hospital by ambulance, where he is in a critical, but stable condition.

Normal traffic resumed at around 3.45pm when the roundabout and surrounding roads were all reopened.

Officers have asked for anyone who might have information that could assist in their enquiries, or who saw the incident take place, to call 101 and speak to the collision investigation unit quoting reference number 280 of October 12.