It was an impromptu insurrection. For one brief, ecstatic morning, lone motorists took to Rte. I-66 inside the Capital Beltway, ignoring the highway's car-pooling restrictions and emerging with nary a traffic ticket to tell the tale.

But it will not--repeat not--happen again, say the Virginia state police, who watched in dismay as scores of Washington-bound commuters, lured by erroneous radio and wire service reports, drove onto the restricted highway for a fine-free one-day outing.

"Because of the confusion we chose not to issue $45 traffic tickets to people," said state police 1st Sgt. Dennis Robertson. "But we'll be back."

All the confusion arose after Virginia Gov. Charles S. Robb announced Wednesday that he was temporarily postponing enforcement of car-pooling restrictions for one Rosslyn ramp of the new 10-mile roadway. Arlington motorists had been using a ramp from Lynn Street to what is a tiny segment of eastbound I-66 for more than 15 years, and a spokesman for the governor said the postponement was necessary to inform those commuters about rules limiting rush-hour use of the ramp to vehicles with more than three persons.

Police said the trouble began in earnest at about 6:20 after WTOP aired a report saying that the rush-hour ridership restrictions had been temporarily lifted for the entire 10-mile stretch from the beltway to the Theodore Roosevelt Bridge, prompting scores of eager lone riders to hit the pavement.

WTOP noted its error within minutes and carried a report correcting the mistake, but by 6:30 another radio station, WMAL, was making the incorrect announcement. Morning news announcer Karen Leggett later acknowledged, "I did make the mistake," but she said she didn't know how the error, which she repeated during 7:30 and 8:30 newscasts, had crept into her copy.

The Associated Press also sent out an incorrect report yesterday morning, but Richmond bureau chief Bob Gallimore said he doubted that AP had been the source of all the confusion. The reason was, Gallimore said, that the AP's erroneous report probably arrived at the two radio stations after they had broadcast their own accounts.

"It was an error in rewriting," he said of the AP mistake. "We're all prone to error, and beyond that I can't really explain it."

By the time the rush hour ended at 9 a.m., state police reported I-66 traffic had been swelled noticeably by solitary drivers, who outnumbered their car-pooling counterparts. And on the Lynn Street ramp, which had started all the trouble, renegade drivers outnumbered car poolers by an estimated 8 to 1.

Not to worry. Police said they will be writing tickets all along the highway today with the exception of the Lynn Street ramp, where drivers have until Monday to comply with the ridership restrictions.

"If they're in violation of the HOV high-occupancy vehicle restriction, they'll be issued a summons," said Sgt. Robertson. "If tomorrow they told me it was restricted to dog sleds with four Eskimos, I'd enforce it."