Pittsburgh EMS and Firefighters responded to a reported unconscious male below I-376 around 3:15 a.m.
When medics arrived, they located a construction worker receiving aid from other workers on scene.
Witnesses stated a construction vehicle was struck by an 18-wheeler prior to his fall.
Pittsburgh EMS transported the victim to a local hospital in critical condition. He was pronounced at the hospital.
The Pennsylvania State Police are handling the investigation.