Andrew McNaughton (not to be confused with the former Balfour Beatty chief executive of the same name) goes part-time in January. He will continue to act as a consultant to the HS2 executive and board on technical matters. He will also advise both the Department of Transport and other government departments on transport matters.
An announcement on the future leadership of the HS2 technical directorate will be made shortly.
Prof McNaughton was Network Rail chief engineer from 2001 to 2009. He then joined HS2 as chief engineer and was its first official employee. He has since guided the project from concept to the edge of reality.
Prof McNaughton said: "After leading the design and authorisation phases of HS2 for the last nine years I am stepping back from a full time executive leadership function to this more strategic role which, I am delighted to say, will continue my strong link with HS2 whilst also giving me more freedom to advise the government here, and others elsewhere, on both high speed railway development, and wider transport issues."
HS2 chief executive Mark Thurston said: "Andrew was not only our first employee, but has also been an inspiration to many of those who have joined since. He has been critical in establishing the project and in recruiting the highly talented team that will carry his and many others' work through to fruition. We will continue to lean heavily on his expertise, at the same time as benefiting from the perspective Andrew gains from his work with other organisations."