A decade and a half ago, research requested by Congress highlighted warning systems as a promising way to get more back-seat passengers to fasten their seat belts.

Over 10 years ago, safety advocacy groups formally asked the government to write rules requiring the warnings. They argued warnings could help save hundreds of lives each year, many of them children.

In 2012, Congress told regulators to get on it, asking for a rule within three years.

This fall, the National Highway Traffic Safety Administration put out an announcement saying they would think about it.

The warning system’s odyssey through the federal bureaucracy highlights the snail’s pace at which consumer groups, the auto industry and former government engineers say new car safety rules travel. Safety advocates say lives are lost in the delays, while the auto industry warns that outdated rules hold back new technology.

“There are certain rules that seem to take significantly longer than anyone could possibly explain,” said Jason Levine, executive director of the Center for Auto Safety. “The rear seat belt reminder rule is amongst the best examples of that.”

And while setting even fairly straightforward rules can take many years, NHTSA is beginning to grapple with a revolution on the roads as automakers develop self-driving vehicles.

The Auto Alliance, which represents many of the world’s biggest car companies, told the Transportation Department in 2017 that at the current pace, merely writing the rules governing the new technology could take decades.

Tracy Hresko Pearl, a law professor at Texas Tech University who studies technology, said the federal government will play a vital role in managing the new technology, but that it presents NHTSA with a major challenge.

“NHTSA has only been dealing with iterative change in vehicles,” Pearl said. “Now we we’ve got a paradigmatic change.”

The Democrats who control the House Energy and Commerce Committee have been pressing NHTSA to explain the hold up on the seat belt rule and a host of others required by Congress.

Rep. Lisa Blunt Rochester (D-Del.) and five of her colleagues wrote to the agency in late October saying lawmakers needed NHTSA to act so lives can be saved.

“It is imperative that NHTSA have the wherewithal to take decisive actions to update its safety standards in a timely manner and fulfill Congressional deadlines,” the representatives wrote.

Traffic deaths have fallen for the past two years but nearly 36,600 people were killed on U.S. roads in 2018.

Members of the Senate Commerce Committee also pressed NHTSA leadership last week on what the agency was doing to ensure driver-assist systems and self-driving cars were being introduced safely.

Acting NHTSA Administrator James Owens told the senators that the agency didn’t want to move right away to establish rules for emerging technologies that help with steering and braking. But he said the agency is considering including new technologies in its safety star rating system.

“If we establish standards too quickly we run the risk of stymieing innovation,” Owens said. “We want to step back. We want to let the innovation occur and the competition occur.”

NHTSA declined to make an official available for an interview and didn’t directly address concerns about the lengthy rule-writing process in written responses to questions.

“While some rulemakings have shorter timelines because they may require less research or address less complicated issues, major rulemakings that require comprehensive research have often taken years to complete,” the agency said.

NHTSA is the nation’s top road-safety agency and its stated mission is to “Save lives, prevent injuries, reduce vehicle-related crashes.”

Much of NHTSA’s work is indeed highly technical, requiring studies by its engineers before carmakers can be ordered to meet new safety standards, former agency employees say. The agency must follow guidelines requiring the benefits of new rules outweigh their costs and then give the public the opportunity to comment on proposals before they are finalized.

But the former employees say the agency is also faced with competing pressures from the safety organizations and industry, while dealing with limited resources.

Two NHTSA offices that help set safety standards governing the millions of new cars sold every year employ 28 people and had six vacancies, the agency recently told Congress. In its response to questions from The Washington Post, the agency said the offices were “finalizing their recruitment efforts this Fall for all their vacancies” and that it has the resources it needs.

Lawrence Hershman, who retired from NHTSA in 2017, said research “can be susceptible to the latest loud noise,” that ideas for new rules can fall victim to in­trac­table internal disagreements and agency priorities respond to shifts in politics.

“Every time there was a change in administration, generally from Democrat to Republican, the emphasis changed,” Hershman said.

Even minuscule changes can take time: Another former engineer described a two-year process to change the code imprinted on tires to show when they were made from three digits to four digits.

The seat belt reminder rule is designed to get more people to buckle up — 25 percent of back-seat passengers go unbelted, a rate far higher than people sitting in the front.

The Auto Alliance wouldn’t comment on the current proposal. In 2010, the group said requiring the reminders would be “premature.”

The Obama administration blew Congress’ deadline for the rule, but consumer advocates say that under the Trump administration, which has a stated focus on cutting regulations, progress on safety standards has been particularly slow.

“They have done no direct, real auto safety rules,” said Amit Narang, a researcher at the liberal advocacy group Public Citizen.

NHTSA bills its proposal to reduce fuel economy standards as a safety measure, arguing it will make new, safer vehicles cheaper so more people will upgrade — a position contested by many experts.

The agency also said it completed work setting a new date by which auto companies must ensure hybrids and electric vehicles can be heard even at low speeds, although the rules themselves were finished in 2016, and updated standards designed to reduce the risk of electric shocks from electric vehicles.

“Almost every rule NHTSA works on will have a safety benefit,” the agency said in its response to The Post.

In its first several months, the Trump administration issued a freeze on new federal rules, as officials weighed how to cut back on regulations.

The rear seat belt reminder rule was listed on a Transportation Department disclosure from December 2016 as being almost ready to publish, but even once the new administration’s freeze was lifted it lay dormant. Safety groups sued the government, asking federal judges to order NHTSA to get to work. They were unsuccessful.

Finally in September, the agency formally said it was thinking about writing a rule. But in keeping with a new policy adopted by the Trump administration that imposes extra steps on proposed rules that might have an economic impact of more than $100 million to implement, the idea that emerged to the public wasn’t even at the starting line.

The public proposal asks for input on a range of technical questions about how the reminders might work, even as it notes that Volvo developed a system in 2009 and now includes it on all the models it sells in the United States.

“They’re taking the longest route possible,” Narang said. “There are absolutely no assurances this will actually reach the finish line by the end of this administration.”

Other ideas backed by safety advocates and the auto industry have advanced slowly or appear to be stalled. Tesla and the Auto Alliance petitioned in 2014 for approval to try using cameras and screens in place of rearview mirrors. Last month, NHTSA issued a formal request for public input on the idea, a potential first step to changing the rules.

And there’s no sign a proposal to require systems that would allow vehicles to communicate safety information to one another wirelessly is advancing. NHTSA has estimated the technology could ultimately save 1,000 lives a year and prevent half a million crashes.

Industry groups have urged the department to continue its work, warning that access to the wireless frequencies needed for the systems could be lost. Indeed, this week FCC Chairman Ajit Pai proposed giving some of the airwaves over to other uses and much of the rest to a different vehicle-safety technology.

NHTSA said it is reviewing some 500 comments on a proposal for the technology issued in the final days of the Obama administration and “other relevant new information to inform our next steps.”

The European Union, meanwhile, has marched ahead. This month it announced a slate of new safety standards that will require advanced technology like automatic braking and systems that help keep drivers in their lanes. Levine said the new measures put Europe a decade ahead of the United States.

“As far as recognizing the need for advanced safety features to be standard and not luxury items, the E.U. appears to be eons ahead,” he said.