Most bicyclists who ride in traffic have experienced the chilling sensation of a vehicle speeding past them just inches away.

Now that's illegal in Pennsylvania.

A state law that took effect at Sunday requires motorists who pass bicyclists to give them at least 4 feet of buffer space. If they cannot do so safely, they must wait to pass. The measure also prohibits what bicyclists call the "right hook" — a vehicle making a sudden right turn directly in the path of a cyclist.

It was sponsored by state Rep. Ron Miller, R-York, and signed into law two months ago by Gov. Tom Corbett.

"Bicycling is great exercise and an effective, efficient mode of transportation, and Pennsylvania has miles of beautiful countryside that can be enjoyed on two wheels," Miller said in a statement on his website. "We need to do all that we can to promote the activity and protect bike enthusiasts through legislation that makes it safer for them to enjoy their sport."

Most Lehigh Valley bicyclists and cycling advocates interviewed welcomed the new law even as they wondered whether it would make much difference in a practical sense and questioned how effectively it can be enforced.

"It's the right thing to do, but is it going to have any practical benefit? I doubt it," said Jack Helffrich, of Upper Macungie Township, president of the Lehigh Valley Wheelmen. Still, he said, "It's better than nothing."

"I'm very happy that this law goes into effect," said Roy Young of Lower Saucon Township, a cyclist active in the Coalition for Appropriate Transportation. "The heart and soul of [the law] is, 'Please go around [cyclists] and don't squeeze by.' I think that's great," Young said.

Deb Burns of Orefield drives and bicycles on area roads, and finds the law wasteful and titled toward cyclists and against drivers, who she pointed out in an email pay "car insurance to drive on those roads and pay for registration tags."

Burns gets upset at cyclists who "ride side-by-side in packs [of two or three abreast] which makes it extremely difficult to pass. On numerous occasions after following [them] for five minutes and then passing carefully on these winding, two-lane roads, I asked them to share the road as I pass, and I get 'the finger'."

Said Steve Pohowsky, bicycle/pedestrian coordinator for the state Department of Transportation's regional District 5: "I'd have to see it in practice" for a time to judge the law's effectiveness.

The law requires cyclists traveling at below the normal speed of traffic to use the right lane or to stay "as close as practicable to the right-hand curb or edge of the roadway" except when passing another vehicle or preparing for a left turn. It allows them to move away from the curb to avoid hazards like potholes or debris.

The key section for motorists states: "The driver of a motor vehicle overtaking a pedalcycle proceeding in the same direction shall pass to the left of the pedalcycle within not less than 4 feet at a careful and prudent reduced speed." Violations are summary offenses that carry a $25 fine.

The law allows drivers on two-lane roads to cross the center line in overtaking a bicycle if there is no oncoming traffic.

Pennsylvania is the 19th state to enact a law requiring a buffer zone when motor vehicles pass bicycles, Miller said.

What to do

Behind the wheel:

Wait to pass until you can leave a 4-foot buffer between your vehicle and the bicycle.

On a bicycle:

Stay "as close as practicable" to right side of roadway unless turning left or avoiding a roadside hazard.