Road users are being urged to avoid a closed section of State Highway 76/Christchurch Southern Motorway as congestion builds after a serious crash.

State Highway 76/Christchurch Southern Motorway is close to westbound traffic near the Curletts Road onramp. Eastbound traffic lanes remain open, and a detour is available via the Curletts Road onramp.

Police say the crash involved a car and truck at around 3pm today, and one person was reported to be in a serious condition.

People can stay up to date on the road status at the Journey Planner site.