He said: "There has been a fundamental readdressing of the core specifications of the West Coast Main Line. There now needs to be a greater understanding of other major rail projects."
Armitt said the rising costs of the West Coast Main Line were the result of constantly changing targets and specifications. He said the priority was to meet the Strategic Rail Authority and properly preplan other problematic schemes.
"Design specifications for projects need to be agreed with architects and clients before a job begins, carried out until completion and then not fundamentally changed or added to," Armitt said.
He added that 85% of work on the west coast project was renewal and only 15% would increase the speed of the trains.
Armitt emphasised that the safety of track workers would be a priority. He said that in December he would be launching a code of practice on "red zone working" – working on live tracks – as four workers had died last year carrying out maintenance work.
Our contractors have the skills and resources and their own profit driver. That is vitally important to get best value
John Armitt, chief executive, Network Rail
The code would mean that work would be carried out on live tracks only when it was essential. "To me, it is vitally important to improve the safety of track workers and to get consistent and improved quality by controlling how and when work is done," he said.
Armitt also backed the use of special purpose vehicles to fund large projects. He said: "The PFI debate relates directly to SPVs as a way of financing enhancements on the railways. I'm sure it can be done; it will require pragmatism by everyone involved in balancing the risks needed to be taken on by the SPV."
Armitt rejected calls for maintenance work to be brought in-house.
He said: "I do not believe that to be the right course. I regard our contractors as having the skills and resources and their own profit driver.
"That is vitally important to get the best value of work from our contractors."