WASHINGTON — The National Transportation Safety Board unveiled a wish list Wednesday for improvements in regulation that it hopes will be carried out this year.

NTSB Chairman Christopher Hart said full implementation of Positive Train Control, a railroad safety system designed to automatically slow trains down before they crash or derail, is a top objective in 2016.

After 25 people died in a head-on rail collision in Chatsworth, Calif. in 2008 — a crash NTSB determined could have been prevented through Positive Train Control — Congress mandated that the safety system be installed on most of the country’s rail lines by 2015. But railroads missed that deadline and Congress extended it to 2018.

“As a result,” Hart said, “much of our rail infrastructure remains unprotected by PTC. Every PTC preventable accident, death and injury on tracks and trains affected by the law will be a direct result of the missed 2015 deadline.”

Since 2008, Hart said there have been at least 11 preventable freight rail accidents and at least two preventable passenger rail accidents, including the Amtrak derailment in Philadelphia last year that killed eight and injured more than 200.

“It’s very frustrating,” said board member Robert Sumwalt, “and it’s sad to go to accidents where we keep seeing the same thing and we know there’s technology that could have prevented that crash.”

Sumwalt said that railroads have already invested about $6 billion into implementing Positive Train Control, and “there’s a lot of people working on this.”

“But it’s critical that this system be implemented as soon as possible,” Sumwalt continued, noting that railroads have already had seven years to get the job done. “Is it going to take another five years or another three years for it to be implemented? And if that’s the case, that’s unacceptable.”

“All the issues on this list are difficult … that’s why they are on this list, because they are going to require more effort and they are going to require more push from everybody including us,” said Hart. “But having said that, Amtrak, for example, has said the entire northeast corridor is now PTC protected, so we know it’s doable.”