A 16-year-old boy was taken to hospital after paramedics were called to a dual carriageway collision.
They sent a rapid response vehicle, helicopter and ambulance to Hemel Hempstead’s A414 – also known as St Albans Road – at about 1.45pm on Saturday.
The crews treated and sedated the boy and said he was in a serious but stable condition. He was taken to the Luton & Dunstable Hospital by ambulance, and the helicopter escorted him there.
East of England Ambulance Service spokesman Richard Dunne said: “He suffered a fractured limb and potential spinal injuries.”