SHENZHEN—Gan Liping pumped her bike across a busy street, racing to beat a crossing light before it turned red. She didn’t make it. Immediately, her face popped up on two video screens above the street. “Jaywalkers will be captured using facial-recognition technology,” the screens said.Facial-recognition technology, once a specter of dystopian science fiction, is becoming a feature of daily life in China, where authorities are using it on streets, in subway stations, at airports and at border crossings in a vast experiment in social engineering. Their goal: to influence behavior and identify lawbreakers.Ms. Gan, 31 years old, had been caught on camera crossing illegally here once before, allowing the system to match her two images. Text displayed on the crosswalk screens identified her as a repeat offender.