Road users in Bedfordshire are advised that one lane is closed between the two A6001 junctions on the southbound carriageway near Biggleswade following an incident involving a lorry on Monday.
One lane will remain closed until Friday while an investigation is carried out, repairs take place and the safety barrier is replaced.
The lane closure and 40mph speed limit is necessary for the safety of road users while the barrier is replaced due to the extensive damage caused.
Drivers using this part of the A1 are advised to plan their journeys and allow extra time to reach their destinations.
Live traffic information is available on the Highways Agency’s website and mobile app, and drivers can also listen to traffic bulletins on local radio for updates.