Indeed, the new section of track in DuPont, Wash., near where the Cascades train derailed on Monday, was an old freight line that had been revamped for passenger trains and named the Point Defiance Bypass. Investigators from the N.T.S.B. have not determined what caused the crash or if positive train control would have prevented it. But they said the train was going 80 miles an hour into a curve with a limit of 30 miles an hour, and that, although equipment for the automatic-braking system was in place, it was not yet in use.

On Wednesday, the Pierce County medical examiner’s office identified the third victim of the crash as Benjamin Gran, 40, of Auburn, Wash.

Richard Anderson, co-chief executive of Amtrak, said on Wednesday that the crash was “a wake-up call” and that Amtrak was determined to operate “the safest railroad in the world.”

Installing the safety technology is only one challenge. The system requires operators of trains to be able to communicate instantly and continually with rail company back offices. Those must be connected with the track’s owners so that real-time information about track conditions and switches — or curves requiring a slowdown — can be fed into the system that automatically slows or stop a train as conditions change. And as in many other parts of the nation’s train system, different entities own different pieces. If all three of the components are not harnessed together and working, then none of it works.

The track used by Amtrak between Tacoma and DuPont, for example, is owned by Sound Transit, a regional transportation agency that serves the Seattle metro area. Rachelle Cunningham, a spokeswoman for Sound Transit, said the agency was on schedule to have positive train control installed by the middle of next year. The BNSF Railroad owns most of the rest of the track in the corridor, Ms. Cunningham said, until the Oregon border, at which point, she said, it becomes Union Pacific’s. When asked why the technology was not added in time for the maiden voyage, Sound Transit referred questions to Amtrak and Washington State’s Department of Transportation. Amtrak earlier this week referred questions on the technology to Sound Transit.

Ms. Cunningham said Sound Transit was only responsible for the track components on a part of the system, while Amtrak and other companies were responsible for the equipment on trains, the radio towers and control center.