The railways say a full, safe rollout of the system across that amount of track in such a short period of time is an "impossible task."

"Freight railroads are determined to safely implement PTC, and have been putting vast resources and energy behind efforts to do so," says American Association of Railroads president and CEO Mr Edward R Hamberger. "But the fact is, it's simply impossible to safely install a reliable, fully interoperable PTC system everywhere it is required by the 2015 deadline."

Since the US Congress passed the Rail Safety Improvement Act, which requires the comprehensive adoption of PTC by 2015, US freight railways have spent more than $US 2.7bn on implementation. This includes design, development and testing of the new communications technology, onboard computers, radios and back-office dispatching software which will enable the seamless operation of each railway's system.

The railways have already partially equipped 6072 out of 18,100 locomotives with PTC onboard equipment, equipped 8504 out of 37,512 wayside locations with PTC wayside interface units, and acquired 2775 of the 56,035 20Mhz base, wayside and locomotive radios required. Many of the Class 1 railways have also committed substantial sums to PTC implementation in their 2013 capital investment plans; CSX will spend $US 325m, Norfolk Southern $US 229m, and BNSF $US 250m.

The scale and costs of the project is inevitably the major hurdle to implementation of PTC. Major commuter railways and the Federal Railroad Administration (FRA) have told Congress technological challenges and a scarcity of funds make meeting the deadline extremely unlikely.

Yet some in the industry feel that more can be done to support the project

In her closing remarks at the conference, chairwoman Ms Deborah Hershman picked up on the apparent clash between those looking forward at what can be achieved, and those who were deemed as looking back and picking fault. She commended those "who have worked hard to comply with the mandate" and challenged others to embrace the challenge to improve safety on the network.

"What is hard is when our recommendations go unheeded and we see the same accident over and over again and more lives needlessly cut short," she said. "The technology and the tools to implement PTC are available. Perhaps what we need to hear about is not what can't be done, but what can be done."