Clarence Ditlow, a tireless consumer advocate who spent a lifetime trying to make cars safer, died on Thursday. He was 72.

Ditlow was known for relentlessly pushing automakers and the government to add safety features to cars and to recall vehicles when patterns of trouble emerged. He served as the executive director of the Center for Auto Safety since 1976. The organization is a watchdog group founded by Consumers Union and Ralph Nader in 1970.

He died at George Washington University Hospital in Washington after a year-long fight with cancer.

“Spanning four decades, his work forced the auto industry to make vast improvements in the safety, reliability and fuel efficiency of the vehicles on which Americans depend daily,” the Center for Auto Safety said in a statement today. “In the past seven years alone, the center was the primary force behind the recalls of 7 million Toyotas for sudden acceleration, 2 million Jeeps for fuel tank fires, 11 million GM vehicles for defective ignition switches, and more than 60 million faulty Takata air bag inflators.”

Ditlow was often just as critical of what he viewed to be the National Highway Traffic Safety Administration’s lax oversight of the automotive industry as he was of the automakers themselves. Still, he earned its respect.

NHTSA Administrator Mark Rosekind said in a statement that millions of Americans are driving cars that are safety because of Ditlow’s efforts.

“Clarence dedicated his life’s work to improving the safety of all those who drive or ride in motor vehicles,” Rosekind said. “Clarence was relentless in his pursuits, and whether he was taking the fight to the auto industry, or prodding NHTSA when he felt we weren’t moving fast enough, no one could ever doubt his heartfelt motivation.”

Ditlow and other representatives of the Center for Auto Safety testified more than 50 times before congressional committees about auto safety, warranties and service bulletins, air pollution, consumer protection and fuel economy.

“A tireless champion for consumers, his work has resulted in better government oversight of automakers, the installation of key safety features and the exposure of safety defects in millions of cars, SUVs and other trucks,” Senators Ed Markey, D-Mass., and Richard Blumenthal, D-Conn., said in a joint statement in the Congressional Record of Sept. 29.