Police evacuated Pennsylvania Station yesterday when an unruly customer threw his suitcase against a ticket counter and said a bomb was inside.

The false alarm suspended railroad service by Amtrak and New Jersey Transit for more than an hour, and subway service for 40 minutes, around 12:20 p.m. Customers waited calmly, with luggage in tow, outside the station.

Though train riders seemed to be at ease as they waited outside Penn Station, this month’s London bombings and stepped-up security measures have intensified the debate over how best to secure the open subway system. Transit workers said yesterday they should be trained to play a role in detecting potential threats.

Police would not identify the man who precipitated the evacuation of Penn Station, which is at Seventh Avenue between 32nd and 33rd streets. Witnesses said he was traveling with a girlfriend when he got into an argument with an Amtrak ticket clerk. After threatening to break the windows of the ticketing office, the man left. He returned a few minutes later with a small blue suitcase and allegedly said it contained a bomb, according to an Amtrak spokeswoman, Sarah Swain. He then hurled it at the clerks’ windows.

“Whatever he said, he just flipped out,” one witness, Mel Kinard, 45, said.

Amtrak police quickly arrested the man and ordered the building evacuated, Ms. Swain said. The suitcase was checked and found to contain no explosives. At 1:24 p.m., the passengers were allowed to return to the station.

The evacuation was the first since police began searching bags and large containers on the subways, buses, and ferries in response to Thursday’s second series of bombings of buses and subways in London in 15 days.

Port Authority police will begin implementing a similar policy today to search bags at random at the Port Authority bus station, on Manhattan’s West Side, and outside PATH train entrances and turnstiles on AirTrains at JFK and Newark airports.

The bombings have heightened tensions between the Metropolitan Transportation Authority and the 35,000-member transit union, which has argued for increased security training and an expanded role to help deter threats against the transit system.

The Transport Workers Union, Local 100, feeling underused as a resource to help protect the transit system against terror threats, began its own limited training program yesterday by hiring a former chief security officer at Ben Gurion Airport in Tel Aviv, Rafi Ron, at a cost to the union of about $10,000.

As police have hinted that the bag searches, which are said to cost about $2 million a week, would not continue indefinitely, the president of Local 100, Roger Toussaint, argued that, with the proper training, the permanent, on-site workforce of transit workers could contribute more to the subway’s security.

“We want training that will send a strong message to the terrorists that employees of New York City’s bus and public systems are watching them,” Mr. Toussaint said, adding: “We need more than a temporary solution to a permanent problem.”

Fifty transit workers spent most of the day yesterday in two courses on how to detect potential terrorists, offered by Mr. Ron and his security company, New Age Security Solutions, based outside Washington, D.C. The instructors, all veterans of Israel’s security forces, trained the various subway conductors, motormen, bus operators, and station agents on how to identify potential threats by isolating suspicious behavior – such as wearing a winter coat in the summer – rather than focusing on a person’s ethnicity. The technique, Mr. Ron said, would help to “screen people from a crowd” on the subway and reduce the tendency to profile by race, which he said was not a reasonable form of detection. He noted that the worst attack on Israeli airports came at the hands of Japanese terrorists in 1972.

“Employees are a source of security,” Mr. Ron said. “Employees’ eyes are everywhere.”

Mr. Ron asked reporters who attended the class not to divulge details of his instruction, saying that to do so might jeopardize efforts to identify potential terrorists. Still, some workers expressed concern that in New York City, where the abnormal is normal, odd but innocuous behavior could be misconstrued as dangerous.

The MTA said in a statement that the union’s efforts yesterday were a “shameless exploitation of the recent events in London” to advance contract talks. The transit workers’ three-year contract expires in December, and the union has been fighting the authority’s plans to remove clerks from station booths and reduce the number of conductors on trains.

A former director of security for the MTA said the agency had resisted security training for transit workers in the past because officials feared it would increase delays. The MTA’s first director of security, Lou Anemone, who was hired three months after the September 11, 2001, attacks, said that the presidents of the authority’s various subsidiaries felt transit workers would overreact to potential terrorist threats and that training should be reserved for police, firefighters, and other “first responders.”

“They didn’t believe there was a need for it,” Mr. Anemone said, referring to the presidents of New York City Transit, the MetroNorth Railroad, and the Long Island Rail Road. “The argument pushed back at me was that there would be too many false alarms.”

Mr. Anemone, who was fired in May 2003 after he leaked word of a corruption scandal, said that during his tenure, “the MTA viewed everything through the lens of labor contracts.”

The MTA has given more than 44,000 workers “eyes and ears” training and brochures, but transit workers said the training was a one-time experience and the brochure was barely read.

“They think if an operator signs for a brochure, they’ve been trained,” one bus operator, J.P. Patafio, 37, said.

Mr. Ron, who boasts 30 years’ security experience and has helped develop security programs at Boston’s Logan Airport, San Francisco International, and at San Juan, Puerto Rico, said most security programs place too much reliance on technology. “We’re looking for something we can see,” Mr. Ron said.