SALEM — As the commuter rail car she was in filled with smoke, Sharon Stocker sat in a cavewoman Halloween costume by her 15-year-old son Robert, dressed as Batman, waiting for rescue.
The Stockers, of Peabody, had volunteered to be mock passengers for a federally required annual railway drill Sunday morning, in which police and fire officials tested their response to a simulated explosion and fire in Salem on Halloween, when the city fills with visitors.
Stocker, one of about 120 volunteers evacuated from two train cars, said she thought seeing police officers and firefighters train would calm her in case she were ever in a real emergency.
“It could happen anywhere and anytime,” said Stocker, in a leopard-print dress. “So we’d like to know how they’d react to it.”
Officials responded as if a passenger in the last train car had set off a small commercial firework while the train was in a tunnel near the Salem commuter rail station, said Randy Clarke, senior director of security and emergency management for the MBTA.
In the scenario, the firework ignited a seat cushion and filled the car with thick gray vapor — which was generated by a smoke machine.
“We wanted to get the police responding thinking it was terrorism, without it actually being terrorism,” Clarke said.
Seven people feigned injuries, assigned ahead of time, from a head contusion and broken bones to smoke inhalation. Stocker pretended to have minor burns on her hands.
Four of the simulated injuries were considered serious but none were critical, Clarke said. There were no real injuries reported, said Kelly Smith, an MBTA spokeswoman.
Planners picked the drill scenario because it would set off a fire department response and a police investigation, Clarke said.
They chose Salem on Halloween because large groups come to the city for the holiday, and the tunnel near the station because it makes the rescue more complicated. Ambulances and fire trucks could not pull right up to the train.
Officials started planning the exercise in March, Clarke said, before two bombs killed three people and injured more than 260 near the finish line of the Boston Marathon, another large and iconic Massachusetts event.
Last year’s drill had a train crashing into a car, then clipping a fuel tanker in Waltham.
MBTA and Massachusetts Department of Transportation officials, the Salem police and fire departments, and Transit Police officers participated.
Smoke spread into the tunnel as passengers walked through the gravel by the tracks to safety.
Some wore Halloween costumes, in the spirit of the exercise, while others wore shorts and T-shirts to fend off the summer-like heat. One man walked with crutches.
The Department of Homeland Security funded the drill, projected to cost about $10,000.
In the coming weeks, officials will gather information from the police officers, firefighters, and civilian volunteers who participated, looking for ways to improve their response in actual emergencies.
Salem firefighters discovered their radios did not get good reception in the tunnel, said firefighter Richard Thomas.
They also figured another entrance to the tunnel might be an easier way in.
“That’s the beauty of the drill,” Thomas said. “We can find easier access points.”
Trisha Malphrus of Swampscott, who uses a wheelchair, said planners asked her to participate in the exercise to give those who responded more experience moving people with limited mobility, and later get her feedback.
Malphrus praised the Salem firefighters who wrapped her tightly in a sheet so she could not flail her arms, then lifted her off the train in a small wheelchair.
“Their professionalism, and how seriously they took it, and their conversation . . . it was amazing,” she said.
Her husband, David, got lower marks.
“He didn’t do good,” she said. “He was supposed to be looking for his wife.”
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