Mourners comfort one another Monday in New York during the funeral for Laura Finamore, who was killed in the May 12 Amtrak train derailment in Philadelphia. Finamore, 47, was headed home from a memorial service for a college friend's mother.

WASHINGTON — Five years ago, federal accident investigators recommended the government require video cameras in locomotive cabs to record engineers’ actions. But it didn’t happen. Now, that’s left a gap in unraveling last week’s fatal Amtrak derailment.

It’s an old story for the National Transportation Safety Board. Accidents occur, people die and there is a clamor for action. Later, when attention moves elsewhere, recommendations frequently lag for years. Some are never realized.

In the Amtrak crash, the train was equipped with a “black box” data recorder and a camera focused on the track ahead. Information from those devices shows that in the last minute before the crash the train accelerated rapidly, reaching 106 mph just before entering a curve where the speed limit was 50. Maximum braking power was applied in the last few seconds, but it was too late.

The train derailed, leaving eight people dead, about 200 injured and a mangled mess of rail cars.

What investigators would like to know is why the train accelerated. Was it a deliberate act by the engineer? An accident? Or was there some other reason?

Conductor Brandon Bostian, who suffered a head injury in the crash, has told investigators he can’t remember anything after leaving Philadelphia’s 30th Street station, the last stop before the derailment, until after the crash.

It’s exactly the kind of circumstance the NTSB’s recommendation for inward-facing video and sound cameras was supposed to address, says Jim Hall, who was the board’s chairman in the 1990s. It’s not unusual for engineers to be killed in train crashes, or to be seriously injured and not remember details.

“To not have all the investigative tools when people have lost their lives in order to understand what occurred and to prevent it from recurring is a travesty,” Hall said. “The black box can tell us what the controls did, but we don’t know exactly what the operator did.”

Until recently, the Federal Railroad Administration had opposed requiring the cameras, citing concern for the privacy of railroad employees and worrying that the images might be used punitively by railroads. Labor unions representing railroad engineers have also strongly opposed the cameras.