Police are calling for witnesses to the crash which killed Christchurch woman Fyfa Dawson

The 19 year old died after she collided with a concrete truck riding her bike along Springs Road, near the Halswell motorway overbridge, last month.

Detective Sergeant Cameron says they want dash cam footage or information from drivers travelling north on the road at the time

He says footage of the traffic flow in the area would help their investigation - as they continue to establish the cause of the tragedy.