NEWARK, N.J. -- Train service was back on track Friday for tens of thousands of commuters who had endured hours of delays when a cascading power outage shut down service between New York and Washington a day earlier.

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The outage on Amtrak equipment around 8 a.m. Thursday stranded commuters and long-distance passengers in hot, smelly cars, some inside tunnels. Those memories were still on commuters' minds Friday.

"I was in a tunnel for 3½ hours," said Tricia Douglass of Newark as she waited for a train to New York. "It was very hot, no air conditioning, no lights."

But she was in a forgiving mood on Friday. "It happens," she said.

Amtrak reported only one delayed train Friday morning, the start of one of the busiest holiday travel weekends of the year. NJ Transit, Philadelphia-area's SEPTA system and Maryland's MARC transit agency also reported service back to normal.

It was a far cry from Thursday, when some stranded passengers got out and walked along the tracks to the next station.

Cliff Black, an Amtrak spokesman said Friday the investigation was continuing. The problem involved tripping circuit breakers at substations that distribute power, he said.

"We're not sure why they tripped," he said. "It didn't remain localized. Usually it takes more than just a few minutes to correct itself. That's what were investigating. This is extremely unusual."

Power was restored around 10:30 a.m., but delays and cancellations affected service through the evening rush.

The outage prompted cries for change at Amtrak, the nation's federally subsidized passenger railroad, which has been plagued by funding shortages, mechanical problems and management turmoil.

"If there was ever proof that Amtrak is being terribly mismanaged with unqualified people at the helm, this power outage at the height of the morning rush hour is it," said Sen. Charles Schumer, D-N.Y. "This outage, quite literally stopped thousands in their tracks and for a rail service that so many people rely on, this is unacceptable."

Amtrak officials declined to respond to the criticism.

It has never turned a profit in its 35 years of existence, posting an operating loss for 2005 of more than $550 million.

In April 2005, Amtrak had to cancel its Acela Express service because of brake problems with the high-speed trains that carry passengers between Washington, New York and Boston. Full service was not restored until September.

Amtrak president David Gunn was fired in November a few days after the Government Accountability Office -- Congress' auditing arm -- issued a blistering report saying Amtrak needed to improve the way it monitors performance and oversees its finances.

Gunn has said he was fired because he did not approve of the Amtrak board's plans on a host of issues. The board has yet to hire another president.

In 2005, President Bush proposed giving Amtrak no money whatsoever, but Congress approved $1.3 billion for the railway. Amtrak's budget request for the next fiscal year is $1.59 billion, while Bush is calling for $900 million.