And while California can largely start from scratch to build a high-speed line planned to connect Los Angeles and San Francisco by 2029 - though it must overcome legal and funding challenges, including a ruling this week stopping a bond sale - the corridor faces a daunting retrofit.
Building a high-speed rail line on the Northeast Corridor (NEC) is a bit like trying to outfit a log cabin with modern plumbing and electricity, new appliances, a three-car garage, Internet service, and a new kitchen, all without disturbing the occupants.
Nonetheless, planners have mapped several strategies to gradually bring 220 m.p.h. trains to the NEC. They envision 37-minute rides between Philadelphia and New York City, with thousands of new jobs and billions of dollars in economic benefits, as well as reduced highway and airport congestion.
An Amtrak plan last year projected it would cost $151 billion and take until 2040 to develop full high-speed travel between Washington and Boston, with incremental improvements in the meantime.
Before Amtrak can move forward with much of that plan, though, the Federal Railroad Administration must complete its "NEC Future" study, which includes environmental and economic analyses of high-speed rail proposals.
The FRA plans to issue a "record of decision" for the corridor by 2015, which could allow Amtrak or others to proceed.
A new $40 billion proposal by the Regional Plan Association in New York City calls for faster development of high-speed capabilities between Philadelphia and New York, making that 90-mile stretch a showcase for high-speed rail on the East Coast.
Trains could reach 220 m.p.h. on a new 15-mile section between Elizabeth and Edison, N.J., and 160 m.p.h. on an upgraded 24-mile section between New Brunswick, N.J., and Trenton, under the proposal.
Those improvements and others, including new tunnels into Manhattan, could cut the travel time between Philadelphia and New York to 55 minutes by 2025, shaving 10 minutes off the fastest times now offered by Amtrak's Acela Express trains.
Fast, frequent service between Philadelphia and New York would create a "whole new economic geography," said Robert Yaro, president of the Regional Plan Association. "It opens up a world of possibilities for Philadelphians," including jobs, housing, and development.
"Center City becomes the Far West Side, with trees," Yaro said.
But all of the plans require federal funding that does not currently exist, and Congress has balked at bankrolling any ambitious plans for high-speed rail.
Amtrak estimates its plan would require spending $3 billion to $4 billion a year for two decades for the Northeast Corridor, which would be about triple the current level of annual capital funding that Amtrak now gets for the whole country.
Congress repeatedly has rejected the Obama administration's request for $50 billion for high-speed rail over six years, and Amtrak is dependent on annual appropriations from Congress for its survival.
"For railroading to thrive, we do have to have a long-term source of funding," the deputy federal railroad administrator, Karen Hedlund, said last week. "This has not been a good year to ask for anything."
In the meantime, Amtrak is taking some steps toward a possible high-speed future.
Workers are upgrading the 24-mile section between New Brunswick and Trenton to permit Acela Express trains to travel 160 m.p.h. there, up from the current 135.
Those will be the fastest trains in the country, and Amtrak must complete the $450 million upgrade by 2017 under requirements for using federal stimulus funding.
"Quite a bit has been done already, and you'll see a big push starting in 2014," said Drew Galloway, Amtrak's chief of NEC planning and performance.
A new power substation is being built near Trenton, and next year, towers will be erected for new overhead catenary lines to power the electric trains. Track realignments and signal improvements will follow.
Amtrak is using an additional $185 million in federal funds to start work on "Gateway" rail tunnels into Manhattan that are crucial to any eventual high-speed Northeast Corridor.
The money, from Hurricane Sandy relief funds, will be used to build an 800-foot concrete tunnel box under a huge real estate development going up near Penn Station.
The box will preserve the right-of-way for two proposed flood-resistant tunnels designed to provide additional rail service between New Jersey and New York's Penn Station. The Gateway project, including the tunnels, is slated to cost $15 billion and be completed by 2025, though Galloway acknowledges that schedule is "very aggressive."
Amtrak also is joining with the California High-Speed Rail Authority to buy new high-speed trains that can meet many of the requirements for both the Northeast Corridor and the planned California line.
The trains, capable of 220 m.p.h. and with room for at least 400 passengers, would be built at a U.S.-based factory, presumably in California, by an international manufacturer, since there are no American builders of high-speed trains.
The California trains will be wider and lighter than the Amtrak trains, because of the confined spaces and varying electrical demands of the Northeast Corridor, but the trains can share many components.
"The Northeast will benefit from the work we do," said Jeff Morales, chief executive officer of the California High-Speed Rail Authority. "We want to work together. . . . We don't want to be in competition."
BY THE NUMBERS
Miles along the rail corridor between Washington and Boston.
Number of rail passengers who travel each day along the Northeast Corridor.
Number of trains running each day in the Northeast Corridor.
Fastest speed that Acela Express trains now reach. High-speed rail could increase that speed to 220 m.p.h.