Abstract: At 10:45 p.m. on April 22, 2023, Employee #1, a 45-year old male street sweeper operator, was working in a closed work zone. At the time of the incident, the non-construction motor vehicle was traveling on Lake Shore Drive and drove through construction barricades and into an established construction work zone. Employee #1 was struck by the motor vehicle while standing outside of his Street Sweeper inside the work zone. A Site-Specific Traffic Control Plan for the project was designed under the authority of the City of Chicago Department of Transportation. Traffic controls establishing the work zone were provided by the Highway Safety Corporation in accordance with the Site-Specific Traffic Control Plan for the project. The investigation found the Site-Specific Traffic Control Plan and related traffic control measures were consistent with fundamental principles of temporary traffic controls, such as those found in guidance sections of the U.S. Department of Transportation Federal Highway Administration Manual on Uniform Traffic Control Devices (MUTCD) and the State of Illinois Highway Standards for Traffic Control that are incorporated in the Site-Specific Traffic Control Plan prepared for the project by the City of Chicago Department of Transportation.