(CNN) Cyclist Alan Crocker regrets flipping off the driver of the blue pickup that buzzed past him on a recent Saturday morning in Rome, Georgia.
He's not proud of it, and he'll never do it again -- especially now that he knows how unpredictable the response might be.
Crocker was wearing a helmet camera that recorded the driver getting out of his vehicle and knocking him over on his bike. He showed the footage to the Floyd County police officer who responded to his 911 call. According to a police report, the footage convinced the officer that the driver was "the aggressor," refuting his claim that Crocker provoked him by kicking his car.
The driver, who did not return requests for comment, was arrested on charges of assault and battery and released on bail. He is awaiting a court date.
Meanwhile, Crocker wonders whether things would have turned out different if he wasn't wearing his helmet camera that day.
"I was able to show the officer the video right there on the side of road," he said. "It's not every day that there's clear evidence showing a cyclist was mistreated."
It's National Bike to Work Week, but bike-friendly roads are still hard to come by in many states, according to rankings released Monday by the League of American Bicyclists. The uneasy relationship between drivers and cyclists can also keep would-be riders off the road.
It's rare for drivers to respond to bicyclists with intentional acts of aggression. But with more bicycles and cars sharing the road, some cyclists are arming themselves with helmet or mounted cameras for the worst-case scenarios.
"Years of experience with law enforcement teaches most frequent and enthusiastic riders that you unfortunately can't rely on police officers to know the traffic laws as they relate to bikes, or to believe a cyclist's version of what happened," said Andy Clarke, president of the League of American Bicyclists.
"There is a pervasive sense that cyclists shouldn't be in the road or should be in the gutter and therefore are in the wrong or just sort of deserved what was coming to them, so video footage can be quite helpful."
Bike enthusiasts tend to be early adopters of technology, especially if it helps them document (or show off) their rides, Clarke said. Chances are the most hardcore cyclists in your neighborhood have long been donning helmet cameras, GPS trackers or fitness monitors for their rides.
It's rare for a cyclist to successfully use helmet camera footage against a motorist, but Crocker's case is the latest example of a cyclist using a camera to document reckless driving. Much of the footage ends up on online, where a movement is growing to catalog repeat offenders, dangerous roads and intersections and make laws intended to protect cyclists more effective.
Crocker uploaded his video to Close Call Database, where cyclists log incidents involving vehicles. The database catalogs incidents by geography and sends out alerts to users in an area where an incident is reported.
Ernest Ezis launched Close Call Database in December after his own close encounter. He was on a group ride outside Boulder, Colorado, on a two-lane highway with a bike lane. A semi accelerated past them at about 60 mph, so close that the side mirror nearly clipped one of his friends and rattled the rest of them off their bikes.
"You have a few close calls that are really dangerous, but usually you forget about them and move on," he said. "This particular time, I stayed angry, and I wanted to do something about it."
The main goal of the site is to be a centralized database to catch repeat offenders and identify roads that are more dangerous than they might seem. Ezis has come to believe that incidents documented on camera are the best evidence to bring to law enforcement.
"I think you'll be much less likely to pass me at 60 mph and only give me 6 inches of space if you realize that might be caught on camera."
He realizes that most close calls are not malicious or intended to hurt cyclists. But ignorance of laws intended to protect cyclists, like safe passing distances, can be just as deadly.
"Drivers need to realize that when they make a mistake, it's often fatal to the cyclist," he said.
A small share of cyclists use cameras for the express purpose of documenting negligent driving. A YouTube search for "bicycle camera" and related terms yields more videos of Spandex-clad cyclists zipping down mountains than collisions between cars and bicycles.
It's a touchy subject for the cycling community. On one hand, safety and advocacy groups worry that cameras perpetuate the idea that cycling is inherently dangerous or that cameras are prerequisites for bicycle safety.
In fact, sometimes the footage shows that the cyclist wasn't as blameless as he or she thought, said lawyer Peter Wilborn, who specializes in laws relating to cyclists' rights.
Wilborn said he has handled cases in which video helped clients and others in which it hurt them. Overall, the effect is more likely to be positive than negative, he said, but it's not a panacea for easing tensions between cyclists and motorists.
"What's important is infrastructure, and in places with infrastructure accidents go down, ridership goes up, and none of it has to do with special accessories," he said.
But proponents of the cameras say they're key to holding reckless drivers to account where legislation meant to protect cyclists falls short.
As cyclist Craig Davis pointed out, the first "3-foot law" creating a protective barrier around cyclists from cars was passed in Wisconsin in 1973. And yet, in his experience cycling for more than three decades, "no one pays attention to it."
Davis started advocacy group 3FootCycling in 2014 to increase enforcement of safe passing laws. Like the Close Call Database, the group's website lets users log close calls on the road involving vehicles.
The group also has partnered with law enforcement and bicycling groups to lead webinars and campaigns on enforcement of 3-foot laws for commercial drivers and law enforcement officers.
"Education doesn't work. Wearing a T-shirt saying 'three feet, please' doesn't work. So what can we do to change driver behavior?" he asked.
Davis sees bike cameras as "the only way" to change the tide, by providing law enforcement with "irrefutable evidence" in cases of one person's word against another.
Crocker said that drivers in his community are "almost uniformly courteous" and that he has ridden tens of thousands of miles with his helmet camera without incident. But it was worth it to have evidence for the time he needed it, he said.
He hopes cyclists learn a lesson in etiquette, too.
"Flipping people off isn't the best course," he said. "You never know who's in that car."