Carillion has been fined £200,000 following the death of a railway worker in 2012.
In a prosecution brought by the Office of Rail and Road, the firm was found to have breached health and safety laws over the death of Scott Dobson near Saxilby, Lincolnshire.
Carillion was also ordered to pay costs of £37,000 after the ORR found a number of failings in its planning and management following Mr Dobson’s death.
Mr Dobson, from Doncaster, was working on the train line on 4 December 2012 when he was struck by a passing train travelling from Gainsborough to Lincoln.
As part of its statutory duties, the ORR investigated the incident and found that only one of the two railway lines had been blocked while maintenance was being carried out.
According to the ORR, both lines should have been closed to minimise the possibility of workers being struck by passing trains.
The ORR also found a wider failure in Carillion’s decision to allocate site safety responsibilities to Mr Dobson after he had been involved in two other incidents with health and safety implications two months prior to his death.
Carillion pleaded guilty at Lincolnshire Magistrates’ Court on Monday.
HM chief inspector of railways Ian Prosser said: “This accident was wholly avoidable, had Carillion followed health and safety rules set out for the railways.
“Our sympathies are with Mr Dobson’s family. The safety of workers and passengers is a top priority for the regulator, which is why ORR inspectors are out on the railway daily, monitoring to ensure safety isn’t compromised.”
A Carillion spokesman said: “Carillion would again like to express its condolences to the family and friends of Mr Dobson. This tragic accident caused deep sadness and shock to those of us in Carillion and the rest of the industry.
“As the court heard, following the accident we undertook a detailed examination of our safety processes and procedures to identify any lessons which could be learnt from this very sad case and act upon them. We have also made a number of improvements which go beyond current industry standards.
“We go to great lengths to ensure that our workforce understands the importance of safety and they are actively encouraged to raise any concerns they may have, which we always act upon.”