Sir Ian has chaired the company for six years
The chairman of rail maintenance firm Network Rail (NR) will step down next year, he has announced.
Sir Ian McAllister, 65, who has chaired the London-based company for six years, said he will not stand for re-election.
NR was fined a record £14m by the Office of Rail Regulation this year, after engineering work over-ran during the 2007 Christmas and New Year period.
Sir Ian said NR delivered "substantial improvements" in safety, reliability and efficiency in his time as chairman.
"Safety is at record levels, train punctuality is now above 90%, and we are on track to reduce cost by around 30% by the next annual general meeting," he said.
"As the company enters a new phase in its development, it is entirely appropriate that a new chairman helps take the company forward."
NR is responsible for maintaining track, signalling and stations across the UK.
In addition its group finance director, Ron Henderson, has announced his retirement.