DETROIT (Reuters) - CSX Corp CSX.O said it is dealing with service issues even as it forges ahead with a controversial overhaul of its network that has led dozens of trade groups to call for an investigation into disruptions at the No. 3 U.S. railroad.

FILE PHOTO: Hunter Harrison speaks to the economic community at a business luncheon in Toronto, March 2, 2015. REUTERS/Mark Blinch/File Photo

In a letter released by the regulator on Monday, CSX CEO Hunter Harrison laid out the tenets of his “precision scheduled railroading” approach, which he said would improve service, cut costs and better use the railroad’s assets.

But the CEO of the Jacksonville, Florida-based railroad adopted a much more conciliatory tone than in recent communications over service issues at CSX.

Previously, Harrison had responded to criticism of service issues at CSX by blaming pushback from employees to his new plan.

In mid-August, 44 trade groups asked federal regulators to investigate “chronic service failures” at CSX which they said had rippled out across North America’s rail network.

Harrison responded to that with another letter saying those claims were “grossly exaggerated.”

In his Aug. 24 letter to the Surface Transportation Board (STB), CSX’s CEO said that this month the railroad had placed “personnel at challenged field locations to bridge communications gaps and target concerns at the local level.”

The company has also resumed operations at a yard in Avon, Indiana, as CSX “pursue optimal processing efficiency to best serve our customers.”

Harrison is a railroading legend who previously served as CEO of Canadian Pacific Railway Ltd CP.TO and Canadian National Railway Co CNR.TO where he dramatically boosted profits with his "precision scheduled railroading" approach.

“I remain confident that as CSX implements its PSR model, customers will receive a markedly superior service model,” Harrison wrote in his letter to the STB.