Dr. Robert G. Newman, who pioneered methadone maintenance as a safe substitute for heroin and struggled to redefine addiction as a chronic medical condition that cannot be cured, died on Aug. 1 in Manhattan. He was 80.

He was struck by a car in the Bronx in June and never recovered from his injuries, his son, Seiji, said.

A chance elevator encounter inspired Dr. Newman to create the world’s largest methadone maintenance program, establishing it in New York City under Mayor John V. Lindsay in 1970.

As an assistant health commissioner for the city, he devoted his career to destigmatizing opioid addiction and treatment. He also served as president of Beth Israel Medical Center, where he presided over its partnership with St. Luke’s-Roosevelt Hospital Center and other institutions in 1997 to form Continuum Health Partners.