A young motorcyclist was badly hurt when he crashed into a central reservation and was thrown into oncoming traffic.
The man in his 30s was airlifted to hospital where he remains in a serious condition following the collision on Stockley Road in West Drayton, on Tuesday (Sept 1) afternoon.
Hillingdon police officers, London Ambulance Service and London's Air Ambulance were called to the scene, near the junction with Horton Road, at around 3pm.
Detectives from the Serious Collision Investigation Unit are carrying out investigations into the circumstances of the incident.
Officers are appealing for witnesses who may have seen anything to come forward and share any information they might have.
A police spokesperson said: "At this early stage of the investigation it is understood the motorcyclist was travelling northbound on Stockley Road when he collided with the central reservation.
"He was thrown over the reservation towards the southbound traffic; fortunately he was not struck by any vehicles travelling on that carriageway."
No other vehicles are thought to be involved but officers are keeping an open mind.
Next of kin have been informed.
Witnesses can call DC Charlie Pulling from the Roads and Transport Policing Command on 020 8991 9555.
