WASHINGTON — More than a year after federal regulators said they would review their procedures amid a widening General Motors ignition switch recall, the National Highway Traffic Safety Administration has admitted to past mistakes and pledged new action.

NHTSA will increase investigations, make more contact with plaintiffs’ lawyers and question assumptions made by its own personnel and automakers.

The changes come after internal reports that acknowledge that NHTSA’s regulators did not demand more information from GM even after it asked about air bag non-deployments and got incomplete answers or legal justifications as to why GM would not or did not have to respond.

One of the reports also noted that neither GM nor NHTSA regulators fully understood how the ignition switch and the air bags worked in tandem, believing incorrectly that the air bags would still deploy even if the key was inadvertently jostled out of the “run” position during a crash.

That lack of understanding, the report said, led to other possible lines of inquiry being disregarded, even when they were suggested by outside investigators. And even as NHTSA conducted its own post-crash investigations into instances where air bags did not deploy and attempted to detect trends, information inside the agency was not always shared across its divisions.

No one has been disciplined or fired inside NHTSA, Administrator Mark Rosekind said last week, adding that he believes no single person should be blamed.

But the safety agency needs to be more proactive, which has led to the initiatives announced Friday that stemmed from two internal reports.

“With small exceptions, all of these improvements are under way,” said Rosekind, who was not heading the agency when the internal review was ordered by Transportation Secretary Anthony Foxx last year but nonetheless characterized it as an exercise in “tough self-examination” he expects will pay off.

The first agency report is a recitation of the facts of the GM case, in which regulators bared their own mistakes while making it clear the automaker was mostly at fault for not communicating information about a defect that has since been linked to 109 deaths and hundreds of injuries.

In the second report, NHTSA performed what it described as a “workforce assessment” designed to show Congress and the public the sort of funding and personnel increases its Office of Defects Investigations needs if it is to make “a much larger and more proactive presence in the automotive safety arena.”

That “new paradigm” — calling for 380 new employees and nearly $90 million in additional spending, is unlikely to draw much support in a Republican-led Congress that, so far, is balking at the substantially smaller request in next year’s budget proposal for NHTSA.

The first report, however — titled “NHTSA’s Path Forward” — came with a clear promise that the agency will do what it can to increase defect detection and oversight of automakers with existing resources, recognizing that while GM could have been more forthcoming, its regulators may have unintentionally dismissed routes of inquiry or not shared information among its divisions that could have located the problem.

Where it can, NHTSA is “already improving its systems for identifying and addressing vehicle safety defects,” Rosekind said, including ensuring that it “challenges its assumptions and explores a broad range of alternate theories” and requiring investigators to better understand how vehicle systems interact.

He also said the agency is working on improving internal communications and information sharing and would like to extend an aspect of the consent order it reached with GM — requiring the automaker to let it know about any potential safety issue its looking at — industry-wide, if possible.

The 24-page “Path Forward” report outlines several other steps the agency has taken or plans to take, including putting automakers on notice even before an investigation is opened that it is monitoring a high-hazard issue, creating a regulatory record and letting manufacturers know of their responsibilities to provide timely data.

The agency would also spell out early warning reporting requirements for automakers and has already implemented changes to its Office of Defects Investigation, requiring automakers to provide their opinions as to the cause of a crash and provide documents revealing settlements involving lawsuits.

It also said the agency’s Office of Chief Counsel will make more contact with plaintiffs’ attorneys to gather more information about possible defects — a particular area where federal regulators are often kept in the dark.