Washington-bound rush-hour commuters on Rte. I-66 got another break from police yesterday and Arlington motorists received some more good news from Virginia Gov. Charles S. Robb.

State highway officials announced late yesterday that they were retreating from an earlier decision and would open two controversial Rosslyn ramps to the highway "to all traffic at all times."

Earlier in the day state police, for the second day in a row, suspended enforcement of restrictions limiting morning rush hour use of the 10 miles of I-66 inside the Capital Beltway to carpools with more than three passengers.

State officials attributed both actions to the confusion and anger of Northern Virginia motorists. "I don't think there's any question that public requests resulted in the state taking another look at the restrictions" on the ramps, said Albert Coates, spokesman for the Virginia Department of Highways and Transportation.

The two Rosslyn ramps, which have been open for the past 15 years, provided North Arlington commuters direct access inbound and outbound to a small stretch of I-66 that joins the Theodore Roosevelt Bridge. But rush-hour restrictions on the newly opened portion of I-66 closed the ramps to use by carpoolers during weekday rush hours, an action that angered hundreds of motorists.

Coates said scores of Northern Virginia residents have been calling local and state officials, including Robb and Rep. Frank R. Wolf (R-Va.), to complain. "It was those calls that prompted the governor to get involved," Coates said last night.

State police decided earlier yesterday against enforcing rules limiting morning rush hour access to the road to carpools after many lone motorists took to the roadway, saying they remained confused about the restrictions.

"We gave them the benefit of a very slim doubt," said Police 1st Sgt. Dennis Robertson. "Some of them," he said, "may have just taken advantage of the situation."

Police had planned to ticket violators yesterday. But early in the rush hour many lone motorists who were stopped by police said they misunderstood reports about who could use the highway. As a result, those drivers, who outnumbered the carpoolers 3 to 1, got off with warnings.

Roberston said that Monday morning police will begin ticketing drivers who violate the carpool rules.

On Wednesday, Robb announced he would postpone enforcement of the carpool rules only for the Lynn Street ramp in Rosslyn, which long has been used by commuters. A wire service and some radio stations erroneously reported Thursday that the restrictions had been lifted for the entire 10 miles of the highway inside the beltway, leading so many single motorists to take to the highway that police suspended enforcement of the rules.

Separately, Vienna town officials said they had sent a letter to the Department of Transportation protesting the rush-hour restrictions.