By Kate McNeil

Try, just try, to turn right onto West 256th Street from Mosholu Avenue around 8 a.m. and Brian Hallinan will be waiting to stop you.

"People have choice words and choice sign language for me," Mr. Hallinan said. "I tell them, 'Have a nice day.'"

Traffic around Riverdale schools is notoriously bad, but the Robert J. Christen School, PS 81 - situated between Mosholu and Riverdale avenues - just might rank the worst.

In an effort to ease congestion on West 256th Street during school drop-off hours, the city Department of Transportation posted a sign prohibiting right turns from Mosholu Avenue on school days from 7 to 9:30 a.m. about a year ago.

But, Mr. Hallinan said, many drivers disregard it, causing a mess of cars and school buses.

That's what led him and another vigilant dad, Ralph Waldow, to take matters into their own hands. For the past three weeks, the dads do their duty by standing in the West 256th Street crosswalk to block westbound traffic.

"We do a round robin," Mr. Hallinan said, standing in the rain on Nov. 15. "I'll go one day, he'll go the next."

Around 9 a.m., Mr. Hallinan left his post to catch a bus to his job in Manhattan.

"Once I picked up the cone and left, people were turning right again," he said. "I don't think people see the sign."

PS 81 parent association co-president Courtney White brought up the school's traffic woes to Community Board 8 members at the Nov. 13 meeting.

"This is nothing new," said Brad Trebach, chairman of the board's traffic and transportation committee. "There are negligent parents who double, even triple, park to drop-off their kids. I remember this going on in the Nixon administration." (In fact, last school year, PS 81 parents were infuriated when traffic agents slapped doubled- parked cars with tickets.)

Mr. Trebach forwarded the parents' recent complaints onto Constance Moran, Bronx commissioner of the Department of Transportation.

"We're just awaiting her reply," he said.

Mr. Hallinan said he hopes something - a flashing yellow light, a larger sign or even a crossing guard - will be implemented before winter comes.

Debra Cantor, a West 256th Street resident and PS 81 parent, said she is "late to work day after day" because parents block her driveway every morning.

"It's just horrendous," she said. "These people are arrogant and hostile. They come up with a million excuses to turn right there. The only thing that has worked has been these dads."

"I've been told by many that there are concerns around many schools and that PS 81 has brought up issues for about a decade," Ms. White said in an e-mail. "Several ask, 'Why bother?' Working on behalf of the PA, we simply can't ignore [them]."