The incident occurred at about 11:55 p.m. in the inbound lanes of I-55 at Damen Avenue.
Police said the victim was walking along the expressway when he was struck and killed. It is not known why the person was on the expressway.
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The driver who struck the pedestrian stopped at the scene and was not hurt, police said.
Police had closed a portion of the expressway, with traffic being diverted off at California. Lanes were back open after 5 a.m.
The driver of the car who struck the pedestrian stopped. He was not hurt.