Financially troubled Colonial Transit Co., which serves Northern Virginia's outer suburbs, has been saying for months that it needs a huge rate increase to survive.

This week it got the increase.

But yesterday, Colonial president Gary Penn said the line couldn't afford to accept the increase, which would boost commuter fares as much as 94 percent.

The reason: Colonial says it is faced with "having half the riders walk off the bus."

The Interstate Commerce Commission will rule today on Colonials' request for less than half of the increase that the agency had authorized on Wednesday.Penn said he hopes that the ICC's action will appease the line's 2,000 commuters some of whom have threatened to abandon his buses if the 94 percent increase becomes effective Monday.

"If we go with the full increase, we would have a serious problem surviving," Penn said yesterday. "I would say we would lose half our passengers."

Penn said in an interview that he never anticipated that the ICC would grant the full 94 percent increase.

Many Virginia commuters have already left Colonial to form their own van pools because they claim the bus line is charging too much for service and its buses are unreliable, old and lack air conditioning.

Anticipation of the rate increase has sparked an upsurge in van pools, which have been growing in popularity since last winter. "What commuters are doing is taking this into their own hands," said George Duke, a Fredericksberg resident who works at the Justice Department and commutes 110 miles daily. Duke said he and a partner picked up a new van yesterday and plan to start their own van pool Monday.

"Our incentive is that we'll have a better time schedule, better equipment and more comfort than the bus company can provide," Duke said.

Colonial now handles about 4,000 passenger trips per day between Prince William County and Fredericksburg and the Washington area.

Albert H. Fitzgerald, chairman of the ICC's suspension board which had ruled on the rate increase, said that unless the ICC commissioners rule otherwise, Colonial will have no choice but to implement the 94 percent increase on Monday. ICC tariffs cannot be changed within 30 days from the time they are posted, he said.

A 94 percent increase would raise the cost of weekly five roundtrip fares from Dale City to Washington from $12.45 to $18.05 and the weekly fare, from Fredericksburg from $16.20 to $31.40, Penn said. The 45 percent increase would put the Dale City weekly fare at $18.05 and the Fredericksburg fare at $23.50. The line now has approximately 50 different fare schedules in use.

Penn was scheduled to be one of several participants last night at a meeting in Prince William County to discuss various alternatives to the public transportation crisis for Washington commuters.

"This is not a problem we can solve in a year or two," said Grace Dupont, chairman of the Prince William County Consumer Protection Commission, which called the meeting.

"Consumer transportation is not profit-making. Either the commuter is going to have to pay the total operating cost or the government is going to have to subsidize it. We're meeting to see just what our options are."