Anthony Noceti cleaned up his 2000 Harley-Davidson, polished it, grabbed a helmet and headed to a nearby gas station one recent morning. It was clear and sunny — a perfect day for a ride.

But as the San Pedro man was about to pump gas into the bike, his attitude quickly soured.

“I remember seeing him,” Noceti recalled later. “He was like 400 yards away. How did he know my helmet was illegal from down there?”

Noceti soon found himself face to face with Los Angeles County Sheriff’s Deputy Christopher Knox, a veteran traffic investigator who is about to call it a career after 31 years on the force.

“I turned left in front of him,” Noceti said. “I went to the pump and all of a sudden, there he was with his lights on.”

Knox, 53, is one of the few deputies people around the South Bay know. He has written tens of thousands of citations, investigated hundreds of traffic collisions and arrested 1,945 people, including 300 for driving under the influence.

“I am passionate about traffic safety because I don’t like going to crashes and seeing people that are injured or killed,” Knox said. “About once a month, someone on the Peninsula dies in a traffic collision from various causes such as speeding, reckless driving, DUI, frail drivers, etc.”

Assigned to the Lomita sheriff’s station, Knox is specifically tasked to work traffic enforcement in Rancho Palos Verdes, Rolling Hills Estates and Rolling Hills. Each city pays for his services as part of their contracts with the county, and Knox spends a portion of each shift in each city.

“People, they know who Chris Knox is,” Rancho Palos Verdes Mayor Jim Knight said. “It’s a local joke: ‘Watch out, he’s always lurking out there.’ ”

Knox’s station commander, Capt. Blaine Bolin, said the deputy makes an impact whether he’s working or not. It’s known as “The Knox Factor.”

“We’ve seen where excessive speeds by motorists used to be the norm. Speeds have decreased significantly just due to The Knox Factor,” Bolin said. “There’s a conscious awareness that Deputy Knox is in the area whether he is physically present or not. When the motoring public alters their driving habits because of the reputation of a traffic deputy, that deputy has made quite an impact.”

Knox can quickly rattle off the numbers: Each year in the United States, 33,000 people die in vehicle crashes, including 10,000 each related to driving under the influence, speeding and not wearing seat belts.

“That’s why we do traffic enforcement,” Knox said. “I try to treat everybody well.”

Knox averaged 14 citations a day for various traffic violations. His high was 21, his low is one on a day he was diverted to investigate a crash. Knox has issued tickets in the same day to husbands and wives, to mothers and daughters, and other family combinations.

“Every day I get repeat offenders. Sometimes I recognize them. Sometimes they remind me,” he said. “At least twice, I’ve cited the same person twice in a day.”

Using a patrol car equipped with radar, dash video and audio recorders, Knox has patrolled the Peninsula’s major routes like Western Avenue, Crenshaw and Hawthorne boulevards, Palos Verdes Drive South and the Switchbacks, a long curvy road that descends toward the ocean and is popular among thrill-seeking motorcyclists.

He also carries a camera in the car to record evidence, such as Noceti’s helmet, to take to court, and employed a device that looks like binoculars and uses a laser to focus on a vehicle’s approaching speed.

Knox spent a recent weekday parked on northbound Western Avenue and issued a ticket to a Chinese food delivery driver speeding at 51 mph, but issued a warning to another motorist moving along at the same speed.

“We give warnings every day,” he said.

Knox later pulled over an 18-year-old Rancho Palos Verdes man speeding at 66 mph up Hawthorne Boulevard from the ocean in his father’s BMW 330ci. The young driver’s license was in the works at the Department of Motor Vehicles, but he did not have one. Knox gave him a ticket and advised him to call his mother to come get him because he was not allowed to drive home. His 26-year-old British girlfriend in the passenger seat next to him didn’t have a valid license either.

Knox said he has no quotas and the Sheriff’s Department receives no money from the traffic citation revenue. A small percentage of the ticket revenue goes to the city, but most is collected by the state.

“We do traffic enforcement because writing tickets for things like speeding, red lights, seat belts, cellphones and texting reduces the number of injury collisions,” he said.

Knox said he has received his share of complaints from unhappy motorists, but also gets the occasional positives. Residents in condominium complexes on Western Avenue have thanked him for making it safer for them to pull out onto the road from their driveway.

“People come up to me and say, ‘Thanks for doing your job. Thanks for writing my teenager a ticket,’ ” Knox said.

Noceti wasn’t one of the happy customers. Although he admitted to wearing a helmet not deemed legal for motorcycle riding, he said he was very close to home and not heading out on the highway. He had other legal helmets at home.

In an interview, Noceti described Knox as another word for a donkey and vowed to meet him in court.

“To pick me out of the blue like that, that is unbelievable,” Noceti said. “I’m going to contest it big time. I’m sure there’s other things that he could have been doing that day instead of harassing me over that helmet.”

But Knox, a motorcycle rider injured in a crash with a vehicle in the past, serves on the California Motorcycle Safety Committee and takes helmet laws seriously. The ticket, he said, was for the man’s own good.

“If he gets in a crash with a novelty helmet, he could be killed,” Knox said. “People don’t have to agree with the ticket. They just have to be civil.”

Noceti said he will likely ask the traffic court for extensions, figuring Knox will retire and decide not to confront him in court once he’s gone.

“That’s good he’s going to retire,” Noceti said. “If he wants to play games, he can come to court on his retirement.”

Noceti will likely see Knox there with a photograph of the illegal helmet. Although the deputy will no longer patrol his shifts, he plans to keep working in traffic safety. As a deputy, he conducted presentations for teachers on safe and sober driving and will continue that with a nonprofit devoted to teenage motorists.

“He helps make our roads safer,” Knight said. At the end of the day, I think everybody appreciates the work he has been doing. … He really did reach out and try to educate the community and the kids. I think he genuinely cares about the people and people being safe.”

Knox plans to leave the force Jan. 26. After 31 years, he said, “It’s time to move on.”

His retirement, however, does not mean it’s time for drivers to think The Knox Factor is over and it’s open season for speeding, his captain said. Another deputy will take over.

“Deputy Knox has been instrumental in helping us to teach and train other traffic enforcement deputies,” Bolin said. “We will continue to have traffic enforcement. That will not change.”