A 34-year-old man has been arrested on suspicion of stabbing a pensioner to death in an apparent road-rage attack near Findon, West Sussex.
Donald Lock, 79, was knifed multiple times after he crashed while driving south on the A24 at around 8.40 BST on 16 July.
After he struck the rear of a car that was also travelling south, Lock exited his vehicle and was confronted by the other driver, who stabbed him before driving away.
He received treatment by paramedics but died at the scene.
Sussex Police said a man from Worthing was arrested by armed officers at 2pm BST on 17 July.
Det Supt Adam Hibbert said: "A man is in custody on suspicion of murder.
"I continue to appeal to anyone who witnessed the collision on the A24 at 8.40pm last night, or who may have CCTV or dashboard cameras of the area at that time, to come to assist our investigation."
'My only grandad'
Lock had just celebrated his 55th wedding anniversary with his wife Maureen, and was due to become a great-grandfather for the sixth time. He was a keen cyclist, and had recently been given the all-clear from cancer.
Notes and tributes have been left at the scene. His granddaughter Kirsty left a bouquet and a note that reads: "I just wish I could hug you one last time.
"Grandad, there are no words to express how I'm feeling. I have lost a very special grandad. My only grandad. I love you so much. You will be truly missed by so many people."
Lock's family issued a statement saying "words could not describe" how much he would be missed.
"He was not your typical great-grandfather and was still cycling up to 150 miles per week," the statement read.
"He loved travelling the world with his wife Maureen and he adored his family. He and Maureen had just celebrated their 55th wedding anniversary.
"He was hugely loved by his family and friends and could often be called upon for his cycling or travel advice.
"Words cannot describe how much he will be missed."