General Motors published an article in February on its Chevrolet website trumpeting an achievement certain to help sell a lot of cars.
Its 2014 Chevys had earned more five-star overall safety ratings in a new car assessment program than had any other brand.
The next day, G.M. began recalling millions of its cars for a deadly ignition defect, and by August, six of the eight five-star Chevrolet models had been recalled for a variety of safety issues, including defects in air bags, brakes and steering. Five had been recalled multiple times.
It was an embarrassing turn — but not just for the embattled automaker. The stellar rankings had been awarded by the federal regulatory agency that is mandated by Congress to ensure the safety of automobiles.
The agency, the National Highway Traffic Safety Administration, has a record of missteps that goes well beyond its failure to detect an ignition switch defect in several models of G.M. cars now linked to at least 13 deaths.
An investigation by The New York Times into the agency’s handling of major safety defects over the past decade found that it frequently has been slow to identify problems, tentative to act and reluctant to employ its full legal powers against companies.
The Times analyzed agency correspondence, regulatory documents and public databases and interviewed congressional and executive branch investigators, former agency employees and auto safety experts. It found that in many of the major vehicle safety issues of recent years — including unintended acceleration in Toyotas, fires in Jeep fuel tanks and air bag ruptures in Hondas, as well as the G.M. ignition defect — the agency did not take a leading role until well after the problems had reached a crisis level, safety advocates had sounded alarms and motorists were injured or died.
Not only does the agency spend about as much money rating new cars — a favorite marketing tool for automakers — as it does investigating potentially deadly manufacturing defects, but it also has been so deferential to automakers that it made a key question it poses about fatal accidents optional — a policy it is only now changing after inquiries from The Times.