Three roads are partially closed and drivers have been urged to avoid the area after emergency services rushed to the scene of a three-vehicle crash in Flamstead.
Police were called at around 11.24am to reports of a three-vehicle road traffic collision involving a white Mini Cooper, a silver Ford Focus and a blue IVECO lorry on London Road.
Teams from Hertfordshire Fire and Rescue and the East of England ambulance service also attended the scene.
Officers at the scene have been forced to partially close River Hill, Chequers and Old Watling Street.
There are long delays on the A5183 in both directions, affecting motorists in Flamstead and Markyate.
Drivers have been urged to avoid the area and seek out alternative travel arrangements.
This is a developing story. For the latest updates, please follow our live blog.
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 The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.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