Faster, better passenger train service on the overcrowded Northeast Corridor will require more cooperation - and money - from eight states and the District of Columbia, eight commuter rail agencies, Amtrak, and freight railroads, rail experts said this week.

A new federal law requires the many users of the 457-mile corridor to come up with a cost-sharing plan by October 2014, and local transit authorities such as SEPTA fear that will mean higher costs for them.

States as well are struggling to pay for new Amtrak requirements. For instance, Pennsylvania in March agreed to pay $3.8 million to save passenger train service between Pittsburgh and Harrisburg.

"This kind of financial picture is very troubling," said Byron Comati, director of strategic planning at SEPTA. "Some of the states are going to have real problems with how these numbers shake down."

SEPTA pays Amtrak $38 million a year to use its tracks for several Regional Rail routes. The new federal law means "it's going to cost SEPTA more," Comati said Wednesday at a session sponsored by the American Public Transportation Association, meeting this week in Center City.

"We have to find a way to provide the same level of service" while paying more, Comati said.

The Federal Railroad Administration is studying how to improve passenger service in the Northeast Corridor.

The FRA in April proposed 15 "preliminary alternatives" for upgrading the corridor.

The FRA plans to come up with a "preferred alternative" by mid-2015, complete with cost estimates and possible construction schedules.

The goal is to lay out a feasible plan for investing in the Northeast Corridor through 2040, with proposals for updated equipment, more trains, new stations, and possible new routes.

And a new multistate group, the Northeast Corridor Infrastructure and Operations Advisory Commission, has been established to coordinate planning and cost-sharing among the many users on the corridor between Washington and Boston.

Meredith Slesinger, the group's director of policy and outreach, said Wednesday that the requirement to craft a cost-sharing plan by October 2014 is ambitious. And she said any funding arrangement must result in increased total spending on the corridor, not simply a shifting of federal costs to the states.

Andrew Galloway, chief of Northeast Corridor planning and performance for Amtrak, agreed that "there needs to be some equity that comes out of this."

Amtrak is planning its own upgrades to the corridor, the most ambitious being new tunnels under the Hudson River to link Manhattan's Pennsylvania Station to North Jersey.

Last week, the Obama administration announced that Amtrak will get $185 million in federal funds to advance work on the tunnels.

The money, which will come from Hurricane Sandy relief funds, will be used to build an 800-foot concrete tunnel box under a huge real-estate development going up next to Penn Station.

The box will serve two new flood-resistant "Gateway" tunnels designed to provide additional rail service between New Jersey and Penn Station. The Gateway project, including the tunnels, is slated to cost $15 billion and be completed by 2025.

A congressional field hearing is scheduled for Friday in New York City on the Northeast Corridor and efforts to improve passenger service between Washington and Boston.