WASHINGTON - When Evan Wilder went flying onto the pavement during his bicycle commute one morning, he didn't have time to notice the license plate of the blue pickup truck that had sideswiped him after its driver hurled a curse at him. Nor did a witness driving another car.
But the video camera Wilder had strapped to his head caught the whole episode. After watching a recording of the incident later, Wilder gave the license plate number to the police and a suspect was eventually charged with leaving the scene of an accident.
"Without the video, we wouldn't know who did it," said Wilder, 33, who was bruised and scraped in the crash.
Cyclists have long had a rocky co-existence with motorists and pedestrians, who often criticize bike riders for a confrontational attitude, and for blowing through stop signs or otherwise exempting themselves from the rules of the road. Now small cameras -- the cycling equivalent of the black box on an airplane -- are becoming an intermediary in the relationship, providing high-tech evidence in what is sometimes an ugly contest between people who ride the roads on two wheels and those who use four.
Footage from these cameras has begun to play an invaluable role in police investigations of a small number of hit-and-runs and other incidents around the country, local authorities say. Lawyers who specialize in representing bicyclists say they expect the use of cameras for this purpose to increase as awareness of the devices goes up and their prices, now starting at around $200, come down.
Some riders even argue that the technology will encourage cyclists to keep themselves in check during dust-ups with drivers.
"I know my actions before and after some event are going to be recorded if I'm the one being a jerk," Wilder said. "It makes me want to be careful."
Bicyclists say cameras can also deter motorist harassment, a problem that many complain about and that cities like Los Angeles and Berkeley have sought to combat with new laws.
"It's a fact of life that on American roads that you get punked, cut off purposely, harassed, not once but on a regular basis," said Bob Mionske, a former Olympic cyclist who is now a lawyer representing bicyclists in Portland, Ore. "If motorists start to hear about bikes having cameras, they're going to think twice about running you off the road."
Gary Souza, a cyclist in Sacramento, said something like that happened to him. He wears a camera on his helmet during his 50-minute commute each way between his home and office. He began riding with the device this year after buying a $7,000 velomobile, a three-wheeled recumbent cycle with a shell around it.
"Even though it's insured, if anything happens I figured I wanted to get it on camera," said Souza, who works in information technology for the state of California.
A couple of months ago, Souza said, a motorist became upset after the cyclist crossed in front of his vehicle to make a turn. The driver got out of his car to confront Souza, who pointed to the camera on his head.
"I said, 'Don't be stupid,' " Souza said. "He quickly ran back to his car. I'm certain I avoided a couple blows."
The cameras, which have started to catch on in the past few years, are meant for shooting video and photos while skiing, surfing and doing other sports. Likewise, many cyclists use them to memorialize their rides.