Two other MBTA employees were accused of tampering with the throttle of a train over the last 16 years, a sign that the practice that apparently led a Red Line train to take off without its operator this month was not unprecedented.
In 1999, the MBTA disciplined a Blue Line driver whom a customer spied jamming a telephone receiver in front of the control lever, the agency said. In 2011, MBTA officials disciplined a previous Red Line driver after a customer reported a similar transgression. And in interviews with 10 past and present drivers or transportation officials, several said they have heard whispers of the practice in the past.
"Does everybody do it? I don't think so," said a part-time driver who said she has never manipulated the throttle that way. "But the smart ones, or the ones who've been there long enough, they know more tricks. We do what we have to do in order to get the job done."
David Vazquez, a longtime Red Line driver, was fired from the MBTA last week and is appealing his termination.
After a Red Line train Vazquez was in charge of rumbled through four stations without a driver earlier this month, Governor Charlie Baker and Transportation Secretary Stephanie Pollack said the driver had violated several safety regulations.
The driver appeared to have used a cord to tie the throttle into place, according to an official briefed on preliminary results of an investigation. Tying down that throttle would presumably allow the driver to acceleratethe train without the rigorous task of applying continuous pressure — but it also disables a safety feature meant to stop the train during emergencies.
Transportation officials have said they have no reason to believe that rigging the throttle is widespread and they would look into the practice during a coordinated investigation with the Federal Transit Administration and the Department of Public Utilities.
Of eight former and current drivers interviewed by the Globe, all of whom spoke on condition of anonymity because of fear of retaliation, half said they wouldn't be surprised to find that drivers had learned to alter the controller in some way.
The MBTA previously said it had not disciplined any drivers for tampering with the throttle in the past five years. But Joe Pesaturo, the MBTA spokesman, said the MBTA's investigation into the practice led to a revelation of the 2011 and 1999 incidents.
Pesaturo said officials are still combing through records to determine if there have been other, similar incidents. Such tampering could lead to termination, according to MBTA policies.
"The MBTA strongly condemns any activity that jeopardizes the safety of customers and employees," he wrote in an e-mail.
On older trains, drivers use the throttle, called a Cineston controller, as both an accelerator and a brake. The controller has a "dead man's" safety feature that stops the train if a driver somehow becomes incapacitated: Once downward pressure is no longer being applied, the train stops.
Some employees say they've heard tales of drivers using different contraptions to force the lever into the "forward" mode: pens, homemade devices, even the radio near the driver's seat.
One Red Line driver said she heard about the practice decades ago but does not know how to do it. Another said older workers probably did it — but if drivers do it these days, they'd know to keep mum about it.
In 1999, a livid rider wrote to the MBTA's top officials, US Senator John Kerry, and several other politicians about a Blue Line driver whom he spied jamming a receiver in front of the throttle to keep the train moving. The customer had been taking the Blue Line from Revere Beach during the Fourth of July, and he believed the driver tampered with the throttle so he could adjust his seat to the right height, he said.
"Why did he disable a fail-safe mechanism and endanger passengers?" wrote the customer, who spoke about his letter to the Globe on condition of anonymity out of fear of retaliation. "Is this dangerous procedure done by other MBTA employees?"
The transportation secretary and chairman of the MBTA at the time, Kevin J. Sullivan, wrote back to him and said the driver had been disciplined appropriately, "due to the serious nature of this infraction."
MBTA officials are quick to point out that their trains are safe because of redundant safety features: In addition to the "dead-man's switch," the train also has another emergency brake. Vazquez appeared to override the former and forgot to set the latter, according to an official briefed on the preliminary results of the investigation.
After the MBTA fired Vazquez, his lawyer said it was unlikely that such a veteran worker would bind the controller. Vazquez, a 53-year-old who worked at the MBTA for more than 20 years, has declined to comment.
Despite such incidents, some former MBTA officials and drivers believe the tampered throttle is completely out of the ordinary. They say such cases are often more folklore than reality.
"You've heard of people doing it, but you haven't actually seen people do it," said John Hogan, a former MBTA official who climbed the ranks from subway train operator, inspector, and dispatcher to director of the operations control center and chief transportation officer at the agency's previous commuter rail operator.
Hogan, who left the commuter rail operator in 2014, said he had heard the rumors and tried to check on his employees. He'd wait in a Wendy's parking lot near the tracks and try to spot a driver reading a newspaper or otherwise goofing off — enabled by a rigged throttle.
"Working there almost 30 years, never did I catch anyone," he said. "And I was a sneak."
A retired driver who spent more than two decades on the line described tampering with the throttle as unthinkable. In this age of ubiquitous camera phones and surveillance cameras in stations, he said, it would be difficult to get away with such a move. Curious customers glancing into the cab could easily snap a picture, snatching away the operator's well-paying job at the same time.
Sometimes, he said, an inspector or a supervisor will hitch a ride on a train to get from one station to the next — and if that person catches the driver, the operator is almost certainly fired.
No driver interviewed by the Globe described the practice as common, and all were quick to point out the same thing: Even if they could imagine colleagues tampering with the throttle, they would never deploy the shortcut themselves.
"I know personally, myself, I don't do it, because I'm a scaredy cat," said the part-time Red Line driver.
But she also said some drivers could simply be finding ways to adapt to a thankless job. Though employees often come under fire for being handsomely compensated by public employee standards, drivers describe the work as grueling with long, monotonous shifts devoid of bathroom breaks, music, or other distractions.
Such excuses don't matter to the customer who was shocked by the Blue Line driver's actions 16 years ago. The MBTA has replaced most of the cars on the Blue Line since then, and the new trains don't use a Cineston controller.
He was surprised by the insistence from drivers that such a practice is nearly unheard of — and not only because he has seen it with his own eyes.
"It would be statistically impossible if it didn't happen," he said.