A 25-MEMBER ADVISORY GROUP that has been studying the future of commuter rail for the last 18 months presented a fairly united front to state transportation officials on Monday, calling for an electrified regional rail system that offers riders more frequent service throughout the day.

T officials had assembled six different options for policymakers to consider, ranging from alternative number one, featuring higher frequency commuter rail provided by diesel locomotives at a price of $1.7 billion in 2020 dollars, to a sixth alternative entitled full transformation, which calls for electrified service at 15 minute intervals on the entire system at an estimated cost of $28.9 billion in 2020 dollars.

At an hour-long meeting with the T’s Fiscal and Management Control Board, members of the advisory group took turns providing their thoughts. While officials from the advisory group quibbled about cost estimates and other issues, the overwhelming consensus favorite of the group was option six.

“We need to think bold,” said Lynn Mayor Thomas McGee. “The sixth choice is the right choice.”

Tim Murray, the head of the Worcester Regional Chamber of Commerce, said he rode into Boston on the train on Monday. He said the number of trips between Worcester and Boston has increased in recent years, but the frequency of service needs to be much greater. “I can’t get on a train now and get back to New England’s second largest city for an hour and a half,” he said after the meeting concluded. “This is not usable because of the frequency.”

Rep. Carol Dykema of Holliston also supported the sixth option, stressing that officials need to think carefully about how to better connect riders to the rail system and the development of the so-called Grand Junction line connecting the north and south sides of the commuter rail system and providing access to Kendall Square.

Transportation Secretary Stephanie Pollack said after listening to the discussion that she wasn’t surprised at the consensus. “What they’re saying is people are interested in both urban rail and regional rail, depending on what communities they are from or representing, and there’s a strong interest in electrification,” she said. “There’s only one alternative that has all three of those elements.”

There was no discussion of how to pay for the commuter rail expansion as part of the meeting.

Joe Aiello, the chair of the Fiscal and Management Control Board, said the panel planned to debate and take a vote on which direction to move commuter rail in next Monday. “It’s going to be live and pretty messy,” he said.

Sen. William Brownsberger of Belmont, a member of the advisory group, said everyone wants to get to a regional rail model with full electrification. “The challenge that we have is to get below that cosmic statement and define a migration path” [to get there,] he said. “The [commuter rail] lines are all different in terms of population densities and job densities that they serve. If you look at the modeling that was done, they all perform very differently. In other words, when you increase service, some see a dramatic increase in ridership, some of them don’t. So you’re going to have to define a pathway that provides service improvements on the lines that are going to respond first, and then we’ll learn from that.”

Murray, the lieutenant governor under Deval Patrick, said the group’s consensus had been emerging in recent weeks. “There’s a lesson from half measures,” he said. “If we had implemented more of the recommendations that Gov. Patrick and I pushed for, I don’t think we’d be at this junction. So there’s a lesson learned.”