Railway guard Christopher McGee has been jailed for five years over the death of teenager Georgia Varley.
The 45-year-old was convicted of the manslaughter of the drunk teenager after he signalled for a train to move as she was leaning against the carriage.
He was found guilty of manslaughter by gross negligence by a unanimous jury at Liverpool Crown Court on Wednesday following a two-week trial.
College student Georgia, 16, had been on a night out in Liverpool with friends when she fell between the train and the platform at the city's James Street station in October last year.
She was three times the legal drink-driving limit and had 0.083mg of the drug mephedrone, or Mcat, in her system at the time, the court heard.
The prosecution said McGee, of Edenhurst Avenue, Wallasey, Wirral, was negligent because he gave the signal to the driver to start the train when Georgia was in contact with the train and was in an "intoxicated state".
McGee, who denied manslaughter, told the jury he thought Georgia was moving away from the train when he gave the signal to depart. He also said he did not know how drunk she was.
But Mr Justice Holroyde told McGee: "In my judgement, the CCTV footage is unequivocal, Georgia Varley was not moving away and she was not showing any sign of moving away.
"She only moved when the movement of the train deprived her of support and caused her to lose balance and fall to her death."
He added: "You did not intend to kill or even injure her, but you displayed an appalling disregard for her safety, and she paid for your criminal negligence with her life."
CCTV footage of the incident was shown to the jury during McGee's trial.
Georgia could be seen mistakenly getting off the train just before 11.30pm, and then turning around and leaning against the side as she realised her friends were still on board.
The Birkenhead Sixth Form College student was then seen to stagger and fall down the gap as the train moved off, before stopping after travelling around 30ft.