A manhunt is under way for a driver who stabbed another motorist to death after a collision between their two cars.
Police said it happened near a garden centre at Rogers Farm on the A24 near Findon, West Sussex.
The 79-year-old victim died at the scene, at about 20:40 BST on Thursday. A murder investigation is under way.
The suspect, described as a tall, skinny, white man in his 30s, is thought to have been driving the car in front of the man who was stabbed.
The attacker is said to have shoulder-length, wavy brown hair and was thought to be driving a pale “old-style” car.
Det Ch Insp Karen Mizzi said: “Officers have been urgently making inquiries overnight to trace the suspect.
“We need to hear from witnesses who saw the collision, the suspect or the car involved, particularly if anyone filmed the incident or saw anyone filming it.”
The A24 remains closed in both directions at the Black Horse pub.