Amtrak is proposing a $7 billion transformation of Union Station, intended to triple passenger capacity and transform the overcrowded station into a high-speed rail hub for the Northeast.

The plan, to be unveiled Wednesday afternoon, calls for doubling the number of trains the station can accommodate and improving the passenger experience at what is the second-busiest Amtrak station in the country, with 100,000 passenger trips per day.

The building’s corridors, concourses and platforms — many dating to the station’s 1907 opening — are regularly jammed during rush hour and major tourist events. The station’s overcrowded tracks hinder Amtrak and regional train operators from adding new trains despite growing demand.

But what the proposal lacks is a vision for financing the plan, which even in stages probably would require huge government funding commitments.

Joseph H. Boardman, Amtrak president and chief executive, said in an interview that the rail line is reimagining what it will take to make rail a vital, viable part of the region’s transportation infrastructure.

Redevelopment plans for Union Station (Gene Thorp/Shalom Baranes Associates)

“The problem that we have is that we’ve got a lack of balance and investment in a mode that moves a lot of people, that is an environmentally responsible mode, and that changes the way that people are going to be able to travel in the future with the technology that is available today,” Boardman said.

Much of Union Station’s expansion would come below ground, where Amtrak plans to add new platforms, tracks and shopping, all of which would enjoy natural light from a 50-foot-wide, 100-foot-long glass-encased main concourse.

Six tracks dedicated to high-speed rail would be added. The high-speed lines could mean travel times as short as 94 minutes to New York City’s Penn Station by 2030 — that’s 66 minutes faster than today’s Acela trains.

District-based developer Akridge also plans a $1.5 billion complex of offices, residential towers and a hotel. The development, to be constructed on a deck built over the tracks behind Union Station, would link Capitol Hill to the NoMa neighborhood.

Dubbed Burnham Place after Union Station architect Daniel Burnham, the 3-million-square-foot project would include a rebuilt H Street bridge and an expanded street grid that would welcome pedestrians to a large new northern entrance to the station. Pedestrian access would be added on all sides of Union Station.

Akridge paid $10 million in 2006 for the right to build above the tracks. “We are now finally getting to see the potential for what Union Station should be,” said Matthew J. Klein, Akridge president.

The agency’s pitch for funding arrives during a period of sharp political disagreement over transportation investment, and Amtrak and its partners have said little about how to raise the $6.5 billion to $7.5 billion it estimates the upgrades would cost.

The federal budget for all surface transportation in recent years has been about $54 billion. As revenues from the long-time transportation funding source — the federal gas tax — have dwindled, some House Republicans have said the money should be devoted primarily to building and maintaining highways and bridges. A long-term transportation bill proposed in the House this year died after urban Republicans broke ranks in opposition to a plan to cut transit out of gas tax revenues.

Boardman said the plan’s intention was to set a course for the station, and that funding discussions would begin once stakeholders agree on its principles.

“If you don’t have a vision for the future, they’re not going to give you the dollars to develop that view of the future,” he said.

Art Guzzetti, vice president of policy and research at the American Public Transportation Association, said the station’s many users may be asked to help foot the cost.

“Certainly you have a lot of people using that station. The rail lines use that station, people use that station, people shop at that station, real estate is around that station. You have a private sector who uses that market there. So I would say you use all of those people. Union Station is an economic generator — how do you turn an economic generator into a revenue raiser?”

District Del. Eleanor Holmes Norton (D), said she expects to be the plan’s biggest advocate on the Hill. “There’s nothing I can do without being able to say look at where they want to go and this amount of money will get them there efficiently,” she said.

In advance of Amtrak’s expected unveiling of its vision Wednesday, local leaders praised the plan for demonstrating how high-speed rail would come to Washington and for addressing some of passengers’ most frequent complaints about Union Station.

The first phase of the overhaul would take place between 2013 and 2017 and cost $200 million to $300 million. It would include replacement of Concourse A, where passengers are often left waiting in winding lines before entering the track, while shoppers and other travelers struggle to pass.

“It is a state-of-the-art design that they are bringing in,” said Victor Hoskins, D.C. deputy mayor for planning and economic development. “It’s going to allow for light and air and flow in the train station like never before.”

John Porcari, U.S. deputy secretary of transportation, said Amtrak had put forth “a strong, clearly articulated vision for the whole Northeast corridor and the Union Station part of it is an integral element of it.”

Former District mayor Anthony Williams, in his new role as chief executive of the Federal City Council, said, ”I’m very impressed with it. I think it’s the vision that the city needs for the next generation of transportation improvements.”