A man has been arrested on suspicion of murdering a 79-year-old driver in a suspected road-rage confrontation.
Don Lock was repeatedly stabbed near Findon, West Sussex, at about 20:40 BST on Thursday.
Sussex Police said a 34-year-old man from Worthing was arrested by armed officers on Friday afternoon.
Mr Lock, who was recently given the all-clear from cancer, was attacked after getting out of his car after a crash with another vehicle on the A24.
He was treated by paramedics but died at the scene.
The cycling enthusiast was due to become a great-grandfather for the sixth time. He and his wife Maureen had just celebrated their 55th wedding anniversary.
Floral tributes have been left by the roadside, including a bouquet from his granddaughter Kirsty with a note that reads: “I just wish I could hug you one last time.”
It also said: “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.”
A woman believed to be widow Maureen Lock was overheard saying: “He was a wonderful husband for 55 years and it finishes like this,” as she left the site of the stabbing with a police liaison officer.
A statement from his family said Mr Lock was full of energy after recently being given the all-clear from cancer.
“He was not your typical great-grandfather and was still cycling up to 150 miles per week,” the statement read.
“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.”
Mr Lock was described as a “kind, gentle, fair man and a good friend” by fellow members of the Worthing Excelsior Cycling Club. He was the editor of the Worthing Wheel magazine for club members.
“His death will be an irreplaceable loss to the club,” said club president Robert Downham.
“Our thoughts are with his family to whom the club will offer our total support at this tragic time.”
People living and working near the scene of the death have described their “shock” over the killing, near a garden centre at Rogers Farm.
“Nothing ever happens round here. And it’s especially shocking that the victim was an old man. Findon is a really lovely little village,” said garden centre worker Laura Muchmore.
“It’s so picturesque and it’s not known for this type of crime.”
Ben Moore, BBC South Today
This has been a very fast moving police operation and officers are still here on the A24, nearly 24 hours since the stabbing happened.
The central reservation, where Mr Lock was stabbed, has been combed extensively by crime scene investigators.
As well as police officers, there have also been a steady stream of other people visiting the site to pay their respects and lay flowers.
Officers have been a few miles down the road where an arrest was made at 14:00 BST by armed police at a dirt track and footpath that led up to the Worthing Golf Club.
Police teams have been carrying out a fingertip search of the area where the stabbing took place and house-to-house inquiries.
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 20:40 BST last night or who may have CCTV or dashboard cameras of the area at that time, to come to assist our investigation.”
Officers made the arrest about half an hour after Det Supt Hibbert made a public appeal for information.