Network Rail has admitted health and safety failings over the 2002 Potters Bar crash, in which seven people died.
The company has said it will plead guilty to charges which were brought over the condition of tracks near the station in Hertfordshire.
Six passengers and a pedestrian died when a train from London to King's Lynn derailed on 10 May 2002.
An inquest last year concluded that a points failure was to blame. The company will be sentenced next month.
Peter Palfrey, chair of the bench at Watford Magistrates' Court, said: "In this case we have decided that the charge is so serious we cannot give punishment at this court."
Speaking outside the court, a Network Rail spokesman said the firm was pleading guilty because it had assumed all of Railtrack's responsibilities and liabilities when it took over the company in October 2002.
But he insisted that travelling by train was now safer than ever: "The railway today is almost unrecognisable since the days of Railtrack and the Potters Bar tragedy.
"All of the recommendations made by both the industry's own formal inquiry and the health and safety investigation have been carried out."
Six passengers - Austen Kark, Emma Knights, Alexander Ogunwusi, Jonael Schickler, Chia Hsin Lin and Chia Chin Wu - were killed in the crash.
The seventh victim, Agnes Quinlivan, was walking nearby and died after she was hit by debris.
More than 70 people were injured.
'An awful ordeal'
The Office of Rail Regulation launched proceedings over alleged breaches of health and safety law after the inquest into the crash last year.
Louise Christian, a solicitor representing some of the victim's families, said there was anger that the process had taken so long.
She expressed concern whether today's events would make a real difference. "The families had to go though an awful ordeal, and what still worries them is whether the safety concerns have been properly addressed for the future," she said.
"This is now a prosecution that can only result in a fine. There's a query whether that will bring about any real accountability, given that Network Rail is a not for profit company."
The Office of Rail Regulation said it was now considering whether it was in the public interest to continue prosecutions against Jarvis, the maintenance firm responsible for the tracks at Potters Bar.
Jarvis was due in court today facing a health and safety charge, but it was not represented when Network Rail entered its intended plea.
There will be another hearing on March 21.