Traffic is at a standstill on the A1(M) between Hatfield and Stevenage.
According to Highways England, the traffic is not moving, with expected delays of 20 minutes.
Normal traffic conditions are expected to resume between 6.30pm and 6.45pm.
Police have not reported a breakdown or collision causing the congestion.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here