Emergency services were called after a car crashed into four cars and a traffic light.
The incident happened on the A41 roundabout at J19 for the M25, near Watford, shortly after 5pm yesterday (Tuesday).
An ambulance was called for one of the drivers.
The cars involved were a black Vauxhall convertible, a white Ford Mondeo, a blue BMW, a black Ford Focus, and an orange Mini Cooper.
There were reports on social media that a motorbike was also involved but it appears this was not the case.
A police spokeswoman said: "Police were called at 5.16pm yesterday to the A41 near the Hunton Bridge Roundabout, Watford, to reports of a multi-vehicle collision.
"One vehicle had collided with four other vehicles and a traffic light.
"An ambulance was called for one of the motorists."
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