As service on Amtrak's critical Boston-to-DC Northeast Corridor returns to normal today, questions remain over the violent derailment of train 188 in Philadelphia last week that left several dead and dozens injured. Triple-digit speeds were reported nearing a curve with a speed limit of just 50, which seems likely to have contributed to the accident — but some sort of object had apparently hit another train along the route, and the NTSB has "not ruled out" the possibility of objects hitting 188 as well.

Still, speed has remained a central focus of the investigation, which has turned the focus to PTC — Positive Train Control, an established technology in the rail industry that uses a system of signals, computers, and GPS to prevent trains from going too fast and colliding with other trains in the event an engineer is incapacitated or makes a mistake. PTC is so promising as a tool for improving rail safety that the federal government has ordered its deployment across broad swaths of the US rail network by the end of 2015. And furthermore, the accident has led the Federal Railroad Administration to demand that Amtrak "immediately" enable automated controls on the segment of track where the disaster occurred.

But David Hughes, a former CEO of Amtrak, argues that the operator hasn't dragged its feet on deploying PTC — in fact, it was "moving as fast as it could," he says in an email to The Verge:

In fact, both Amtrak and the freight railroads have been going full speed in implementing PTC, but there are some formidable challenges. For the freight railroads, when PTC technology was mandated by Congress, the technology to implement it did not exist. So, railroads and the supply industry had to effectively invent it. Everyone agreed that it could be invented, but that takes time and lots of integrity and safety testing. In addition, the system required radio spectrum that wasn't available. So the railroads had to go out and buy up in bits and pieces the radio spectrum to implement PTC. Moreover, even with spectrum, sites for new radio towers were required which had long permitting process. Every tower had to be approved by the local Indian tribe to ensure it wasn't near some sacred site. Permitting was a real mess.

No doubt the railroads felt that PTC did not have enough benefits to justify the $10 [billion] or so in costs, but I believe, as an insider in the railroad industry, that they have moved with all due haste in implementing PTC.

As for Amtrak, the equipment for PTC was already installed in the track at the time of the accident. It had not been made operational because Amtrak had only recently received FCC approval for their use of the spectrum they purchased. So, the timing was really unfortunate, but Amtrak was moving as fast as it could to implement PTC on that curve.

Hughes is correct in saying that the FCC just recently signed off on Amtrak's PTC spectrum in the area: a blog post by the FCC's Roger Sherman confirms that approval came in March of this year, while also noting that railroads must acquire spectrum at auction or from existing license holders "by law" — basically, the FCC can't pull new spectrum to meet the PTC mandate out of thin air. None of that is to say that an earlier request for approval from Amtrak couldn't have necessarily gotten PTC deployed to that curve more quickly, however; Sherman says that the FCC signed off on Amtrak's request "just two days after Amtrak submitted a final amendment" in March.

It could still be "up to 12 months" before the NTSB issues its final report on the root cause of the crash, the agency reports. Its next update on the investigation is expected later this week.