Amtrak's Acela Express trains now travel up to 150 miles per hour on a short stretch in New England, but the top speed between New York and Washington is 135 miles an hour.
And the train's average speed is considerably lower: On the 319-mile trip between Philadelphia and Boston, Acela averages about 64 miles per hour.
Amtrak last year outlined a $151 billion vision for high-speed travel on the Northeast Corridor, with 220 m.p.h. trains between New York and Washington by about 2030 and between New York and Boston by 2040. That plan envisioned 37-minute trips between Philadelphia and New York.
The Obama administration urged Amtrak and California to develop a joint high-speed train order to attract foreign train manufacturers to build factories in the United States, creating jobs and a new industry here.
In January, Amtrak and the California High-Speed Rail Authority said in a news release that they were "joining forces in the search for proven high-speed-rail train sets currently being manufactured and in commercial service that are capable of operating safely at speeds up to 220 m.p.h. on both Amtrak's Northeast Corridor and on California's developing HSR corridor."
The same month, Amtrak published proposed performance requirements that called for a maximum operating speed of 220 miles per hour, with a maximum test speed of 225 mp.h.
But when Amtrak issued draft specifications for the new trains on Nov. 19, gone were the requirements for 220 m.p.h service on the Northeast Corridor. Instead, the requirements were set for 160 miles per hour.
Rod Diridon, a high-speed-rail expert who is the executive director of the Mineta Transportation Institute in San Jose, said the new Amtrak 160-m.p.h. specification "is sure news to me."
"We all thought the joint specs called for the standard international definition of high-speed rail, which is at least 300 kilometers per hour, or 186 miles per hour, remembering that the most modern of the international trains are indeed traveling 220 m.p.h. in daily service," Diridon said.
An Amtrak spokesman said Friday that the railroad still hoped to eventually run 220 m.p.h. trains between Washington and Boston.
Spokesman Craig Schulz said Amtrak hoped to buy 160-mile-an-hour trains that could be modified in the future to go faster, as the Northeast Corridor was upgraded to permit higher speeds.
Schulz said the "Northeast Corridor infrastructure effectively limits maximum speeds to 160 m.p.h. That will likely be the case for many years - even under the most favorable of assumptions about funding availability for infrastructure improvements.
"Amtrak is seeking new train sets that are immediately capable of operating at speeds up to 160 m.p.h.," Schulz said. "We are working with California to see if we can acquire equipment that cost-effectively meets our short-term operational needs and their long-term operational needs, which would require operations at 220 m.p.h."
"We continue to work toward the goal of 220 m.p.h. service on the NEC, while mindful of the tremendous investment necessary to upgrade the infrastructure to a point that can support such speeds," he said.
Schulz, who noted Acela set a monthly ridership record in October, said Amtrak's "highest priority in this effort to acquire new equipment in expanding current capacity."
He said passengers cared less about top speed than about how long a journey would take.
"It's great to have trains that travel fast, but at the end of the day," he said, "it's trip time that matters most."
By improving tunnels, bridges, tracks, and signals on the corridor, he said, Amtrak could significantly reduce travel times, even with 160 m.p.h. trains.
A spokesman for the Federal Railroad Administration was optimistic that trains could be built to meet both today's limitations and tomorrow's ambitions.
In a statement, spokesman Michael Murray said the FRA "brought Amtrak and the California High-Speed Rail Authority together to facilitate the joint acquisition of lightweight, service-proven train sets with a common platform.
"With only small modifications, we believe this common platform can meet Amtrak's short-term goal of replacing aging Acela equipment and adding new service on today's Northeast Corridor infrastructure, while achieving top speeds of over 200 m.p.h. on future high-speed rail corridors."
Andy Kunz, president of the U.S. High Speed Rail Association, said it should not be too difficult to build a train that could operate at slower speeds on the East Coast than on the West Coast.
"It would be a little like owning a Ferrari that can go 190, but you never drive it more than 60."
Companies involved in building high-speed trains were less sanguine.
"They're realistically two different trains," said one manufacturer, who declined to be named.
Another official of a firm involved in high-speed-rail engineering said the requirements of Amtrak and California now appeared to be "very different."
Amtrak and California hope to issue their joint request for proposals for the new high-speed trains early next year.