After a late-night filibuster, a Senate committee managed to avoid a showdown vote yesterday morning on the touchy question of free parking for members of congress and their staffs.

Following a Senate session that lasted until 3:40 a.m., only six of the 17 members of the Government Affairs Committee showed up for a 10 a.m. hearing on the proposal of Sen. Charles Percy (R-III.) to impose parking fees on legislative and judicial branch employes. Committee rules require that nine members be present to vote on legislation, so the matter was postponed for the second time in a week.

Percy had been promised a hearing yesterday after he agreed not to tack his parking-fee legilation onto a $1.7 billion Metro funding bill that the committee approved Tuesday.

One of the senators at the late-night session who did not show up at the parking-fee hearing was Sen. Charles McC. Mathias (R-Md.), a chief opponet of the fees.

Another opponent, Sen. Ted Stevens (R-Alaska), showed up but used the late-night session as an example of why Capitol Hill workers deserve convenient, free parking.

"I don't want my staffers walking four or five blocks to their cars in the middle of the night. They could get raped," Stevens said.

Percy explained that under his plan, congressional staffers wouldn't have to give up their parking places, just pay for the privilege, as executive branch employes do.

"But they won't pay," said Stevens, "and I don't blame them. There is no reason for this bill."

Percy argued that eliminating free parking on the hill would be "an important symbol" to the nation that Congress is serious about the energy crisis.

"There is no way mass transit can compete against free parking and subsidized gasoline," said Percy, who also favors a tax on gasoline of 50 cents a gallon or more.

Imposing parking fees on Congress, federal judges and their employes also would eliminate the "gross inequities" that have resulted since Nov. 1, when more than 2 million employes of executive branch agencies have had to pay for parking, Percy said. He said the Office of Management and Budget "arleady has evidene" that the president's parking order has resulted in greater use of buses and car pooling.

Although a spokesman for Metro said it has not seen a dramatic change in ridership in the last six weeks, a Percy aide said OMB has reported that more federal workers are applying for car pool permits, that federal parking lots are filling up later, and that some bus lines, especially at the Pentagon, are attracting additional passengers.