Network Rail was fined £1 million on Thursday after it breached health and safety laws at a level crossing where two teenage girls were killed.
Olivia Bazlinton, 14, and Charlotte Thompson, 13, were hit by a train in 2005 as they crossed the tracks at Elsenham station footpath crossing in Essex.
Judge David Turner QC, sentencing at Chelmsford Crown Court, fined the authority responsible for the UK's railway network £1 million and ordered it to pay £60,000 costs.
Olivia and Charlotte were killed on December 3 2005 as they crossed a footpath leading to Elsenham station platform. The crossing was fitted with warning lights and yodel alarms.
A London-to-Cambridge train passed over the crossing with the red lights and yodel sounding - a warning for foot passengers not to cross.
After the train passed, the lights remained on and the alarms continued to sound as another train, travelling from Birmingham to Stansted Airport in Essex, was going to pass through the station.
The girls opened the unlocked wicket gates and walked on to the crossing. They were both struck by the Stansted train and killed.
Last November, the Office of Rail Regulation (ORR) announced that it would prosecute Network Rail over those deaths after reopening its investigation into the accident.
The move came after the Transport Salaried Staffs Association joined the girls' families in demanding a public inquiry amid claims that two safety documents were not disclosed to the Essex coroner at the 2007 inquest into the deaths.
At a hearing in January, Network Rail pleaded guilty to three health and safety breaches.
The authority admitted failing to carry out a sufficient risk assessment, failing to properly control protective measures at the level crossing, and failing to prevent the girls from being exposed to the risks which led to their deaths.
Network Rail was fined £3m in 2011 at St Albans Crown Court after admitting safety breaches involving a set of points which led to a derailment at Potters Bar in Hertfordshire in May 2002, where seven people were killed.
Chelmsford Crown Court heard that Olivia and Charlotte were killed on December 3 2005 as they crossed a footpath leading to Elsenham station platform.
The court was told that the pair "seemed happy" and were chatting and holding hands moments before their deaths.
The crossing was fitted with warning lights and alarms.
A London-to-Cambridge train passed over the crossing with the red lights and yodel sounding - a warning for foot passengers not to cross.
After the train passed, the lights remained on and the alarms continued to sound as another train, travelling from Birmingham to Stansted Airport in Essex, was going to pass through the station.
The girls opened the unlocked wicket gates and walked on to the crossing. They were both struck by the Stansted train and killed.
The court heard that a safety official had raised concerns about the possibility of tragedy in a memorandum in 2001 but the document was not disclosed by Network Rail until last year.
Judge Turner said Network Rail had a "solemn responsibility" for the safety of members of the public, adding: "The company concedes that the procedures or standards in place for conducting level crossing risk assessments before 2005 were deficient.
"The company unreservedly apologises for its failures which contributed to the deaths of these young girls.
"Network Rail, in part by itself and in part through its predecessor Railtrack, failed to ensure that the risks were properly assessed, controlled or managed."
Olivia's mother, Tina Hughes, who clutched an old teddy bear throughout the proceedings, had tears in her eyes when she said: "I didn't really want to come to court.
"I wanted to go to parents' evening and hear the teachers say that Olivia talked too much in class, and sit in the seat when she took her driving test and cling to it, and see her bring a bag of washing home from uni, and watch her walk down the aisle looking like an angel, and look into the eyes of her newborn babies."
She said that if disclosure of key safety documents had come sooner then teenager Katie Littlewood still be alive.
The 15-year-old was hit by a train in January at Johnson's Footpath Crossing in Bishop's Stortford, Hertfordshire.
Her death happened just a few miles down the track from where Olivia and Charlotte were killed six years ago.
Ms Hughes said had the documents been disclosed in time for the inquest of her daughter and Charlotte in 2007, then key safety changes which Network Rail is rolling out would have already been implemented and Katie would not have been killed.
"Had it been done before then Katie would not have died on that crossing and that absolutely breaks my heart," she added.
Olivia's father, Chris Bazlinton, said: "Everybody says 'Has justice been done?' Justice can't be done after you have lost your daughter.
"The process of justice has been done and they have been fined £1 million - it is nothing more than symbolic."
Charlotte's mother, Hilary Thompson, said: "They took our daughters from us and they broke our hearts."
Charlotte's father, Reg Thompson, added: "I do believe because of what has been done, because of what Chris and Tina have done, that Charlie and Liv at least have meant that the railways will be safer.
"What Network Rail have promised to do today in court, which is to spend £130 million on improving safety on level crossings, and the changes that they have already made, have come about because of the terrible thing that happened to our daughters