A bicyclist who police say tracked down and beat another bicyclist for suggesting he get a light for his bike was arrested Thursday.

Dustin K. Dunlavy, 28, of Madison, was arrested on tentative charges of battery and disorderly conduct in connection with the incident, which began about 6:30 p.m. Nov. 26 on South Shore Drive, as Dunlavy and his girlfriend pedaled around bicyclist Colin O'Brien in the dark, police said.

The pair didn't have lights on their bicycles. As they passed, O'Brien, who owns Cronometro, a Williamson Street business that builds custom bicycles, said, "Get a light." That suggestion led to a confrontation that extended all the way to O'Brien's home and driveway where, O'Brien told police, Dunlavy twisted his head and kneed him in the ribs.

Police were aided in tracking the pair by O'Brien's detailed description of the bicyclists and their bicycles, which were distinctive and expensive, said Police Department spokesman Joel DeSpain. The man was riding a Trek Time Trial bike with front-style handlebars.

According to police, "Dunlavy acknowledged he had gotten into a confrontation with (O'Brien) but denied he threw him to the ground or kneed him in the ribs."

Dunlavy told police the two got into a pushing match and he did grab O'Brien by the head but "did not believe this would cause pain as the victim was wearing a bicycle helmet."

Madison Police Officer Scott Reitmeier asked Dunlavy why he did not simply ride away following the "get a light" comment, and Dunlavy responded he felt "extremely insulted by the statement and didn't think anyone had a right to tell him he should have a light on his bike."

State law requires bicyclists to have a light visible from the front for 500 feet and a reflector on the back, said Arthur Ross, the city's bicycle-pedestrian coordinator.

Ross strongly recommends going further.

"You have to do more than just make yourself visible," he said. "You should also allow yourself to be able to see what's ahead of you on the road. Get as strong a light as you can."

DeSpain said getting a good description of the bicycles "played an important part in locating the suspect."

"With the aid of citizens we were able to get a name," he said.

He said the female bicyclist was located and interviewed but "there was no reason to arrest her."

According to O'Brien's statement to police, after telling the bicyclists to get lights for their bikes, the pair passed him and asked O'Brien what he said.

When he repeated, "Get a light," the couple yelled at O'Brien to "mind his own business," and the male bicyclist tried to run O'Brien off the road, police reported. The two then followed O'Brien to the driveway of his South Side home, where the argument continued and the female rider commented that the "victim seemed to have plenty of lights and asked for one," according to police.

O'Brien obliged, giving her a light, according to police, but the woman's companion, "still upset about the original comment, proceeded to clamp his hands around the victim's head," police said.

For bicycle lighting rules and recommendations, go to www.cityofmadison.com and find your way to transportation, then traffic engineering, where a pull-down menu will take you to bicycle information.