Advocates expect it to generate frustration among motorists who don't like encountering slower-moving bikes, but say it will help the majority understand how to navigate safely when encountering riders.

"Some motorists believe that bikes shouldn't be on the road, but by law we're a vehicle just like any vehicle on the road," said Eric Broadwell, a Roswell cyclist and board member of Georgia Bikes!, a statewide advocacy group. The law will also help sympathetic drivers, he said. "Even my wife is nervous when she sees a rider. She doesn't know what to do, and I have to coach her along."

House Bill 101 will clarify things. Prior to its adoption, state law required only that drivers leave a "safe distance" between their vehicle and bikes. Broadwell said the new law basically means motorists must cross the yellow line -- when the oncoming lane is clear, of course -- to pass legally.

The legislation, sponsored by Rep. Doug McKillip, an Athens Republican, originally did not include the distance requirement. Instead, it focused on other cycling minutiae, such as a requirement for rear reflectors (cyclists can now substitute a red light) and the requirement that cyclists ride no more than two abreast (they can now exceed two at certain permitted events).

Then, at the end of the legislative session, Sen. John Albers, a Roswell Republican, tacked on the 3-foot requirement. The firefighter and recreational cyclist said he was inspired by testimony from Kathy Serrano, the widow of cyclist Tony Serrano who was killed in 2004 by a car in Gwinnett County.

Albers was also concerned about the safety of his two children, ages 15 and 8.

"Roswell is a very bicycle-friendly community," he said, "but it's dangerous out there." Albers said his main goal was getting a law on the books as an educational tool so that drivers, over time, would learn to give cyclists wide berth.

Violation is a misdemeanor punishable by fines and jail time. And, advocates say, the 3-foot limit will be relevant in lawsuits stemming from collisions where the old "safe distance" requirement was vague about liability.

Georgia is joining at least 19 other states with 3-foot passing laws, according to the League of American Bicyclists. Karen Morgan, a spokeswoman for AAA, said the automobile advocacy group supports such laws and tries to educate drivers about cyclists.

Serrano said the new law will save lives. Her husband was flung 150 feet up the road when the man driving a car rear-ended him. "He hit him with the right, front headlight," she said, "so obviously three feet wasn't given."