Emergency personnel work at the scene of a deadly train wreck, Wednesday, May 13, 2015, in Philadelphia. The NTSB’s “10 Most Wanted” list for 2016 underscores the need for rail safety. (Patrick Semansky/AP)

The risk of a disastrous tank car explosion in a major city and preventing tragedies like last year’s fatal Amtrak derailment in Philadelphia dominated the discussion Wednesday as the National Transportation Safety Board issued its priorities for 2016.

The NTSB sent a stern message to Congress and federal regulators about the potential consequences of delays in installing automatic-braking technology to prevent high-speed derailments and in replacing rail tank cars that carry volatile flammable loads.

NTSB Chairman Christopher A. Hart invoked the memory of a runaway train that derailed in flames in Lac-Mégantic, Canada, in 2013, killing 47 people and burning down more than 30 buildings.

“We’ve been lucky thus far that derailments involving flammable liquids in America have not yet occurred in a populated area,” Hart said. “But an American version of Lac-Mégantic could happen at any time. Instead of happening out in the middle of a wheat field it could happen in the middle of a big city.”

He said a federal requirement that railroads replace tank cars with a safer generation of tankers by 2025 was “much too long” to wait.

NTSB board member Robert L. Sumwalt, who headed a safety board delegation sent to the Philadelphia Amtrak crash that killed eight and injured more than 200 last May, said a congressional decision to extend the deadline for installing automatic-breaking technology known as Positive Train Control was “very frustrating.”

“Every day that PTC is not in place we run the risk of another Amtrak crash,” Sumwalt said, declining to say whether Congress or the railroads deserved most of the blame. “Is it going to take another five years or another three years for it to be implemented? If that’s the case, that’s unacceptable.”

Federal Railroad Administration head Sarah Feinberg has made clear she intends to hold the railroads to strict deadlines to expedite PTC installation and get the outmoded DOT 111 tank cars replaced.

Ed Greenberg, spokesman for the American Association of Railroads, said PTC is “a full-time focus of the freight rail industry,” which already has spent $6 billion on installation.

“But the reality is this technology is not off-the shelf, it had to be developed from scratch and isn’t just about plugging in or turning on components, it is a complex step-by-step process, both in terms of safety engineering and implementation,” he said.

Hart was unsympathetic to the complexity of the challenge.

“In 2008 after a PTC preventable collision in Chatsworth, California, killed 25 people and injured for than 100, Congress passed a law mandating PTC implementation by the end of 2015,” Hart said, listing the number of accidents it could have prevented since 2008. “Now it’s 2016, and according to the 2008 law, such tragedies should be things of the past, but the railroads missed the deadline. Every PTC preventable accident death and injury on tracks and trains affected by the law will be a direct result of the missed deadline.”

Hart pointed out that Amtrak successfully met the deadline for installation of PTC in the Northeast rail corridor, but most of the big freight rail companies fell far short.

The role of the NTSB is to investigate accidents and make recommendations on safety issues to Congress and federal regulatory agencies.

The NTSB’s Ten Most Wanted list of recommended safety improvements includes:

--Improve federal rail transit safety oversight.

Hart: “We have seen far too many fatalities and injuries on rail mass transit.”

--Promote collision avoidance technology for cars and trucks.

Hart: “Seat belts are standard equipment rather than a luxury option and the same should be true for collision avoidance technologies.

--Eliminate operator distractions.

Hart: “Technology has saved countless lives. [But] “We have recommended prohibiting all cell phone use, including hands free, because a driver’s mind must be on their driving.”

--Prevent loss-of-control by small plane pilots that has killed 1,200 people since 2008.

Hart: “The fatal accident rate has been stubbornly resistent to improvement for many years.”

--Curtail drunk and drugged driving.

Hart: “Recently we are seeing prescribed, over the counter and recreational drugs are exacerbating the problem of impaired driving.”

--Require fitness for duty reports for public vehicle operators.

--Expand use of data recorders on planes, trains, ferries and buses.

--Improve protection of passengers riding in vehicles.

--Reduce fatigue-related accidents.