A nine-year-old boy was airlifted to hospital with serious head injuries after a road traffic collision.
The collision happened on Redbourn Road in Hemel Hempstead, near to the Maylands industrial park, at 1.48pm on Saturday.
For reasons unknown at this stage, a Grey Kia car was involved in a collision with the boy.
He suffered serious head injuries and was airlifted to a hospital in London.
The driver of the vehicle remained at the scene and was uninjured.
Police are now appealing for witnesses following the incident.
PC Helen Carpenter from the Forensic Collision Investigation Unit said: “We are providing support to the family at this time and hope the boy, whose condition is currently described as very serious, improves.
“We are investigating the circumstances of what happened and I am looking to speak to anyone who saw the collision take place or events leading up to it.
“If you have information about the incident, please contact police via the non-emergency number 101.”