A motorcyclist was rushed to hospital with serious injuries after they were involved in a crash.
An air ambulance was among several emergency vehicles called to the A405 in Watford on Saturday.
A Yamaha motorbike and a Ford Mondeo were involved in a collision at the junction with Greenwood Drive.
A photo taken of the scene appears to show the crash took place on the traffic island in the middle of the dual carriageway.
Hertfordshire Constabulary and the East of England Ambulance Service (EEAS) received a call at 12.30pm.
The Essex & Herts Air Ambulance also received a call, with the helicopter landing on a field behind Woodside Leisure Park.
The air ambulance attended, landing near to the scene of the crash. Credit: Dennis Brookes
An EEAS spokeswoman said: "We were called just after 12.30 with reports of a road traffic accident. We sent two ambulances, a response car and an air ambulance. One patient was transferred to St Marys hospital for further treatment."
The A405 was shut in both directions for a couple of hours, with the road fully reopening at 3pm.
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 The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.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