Who has the authority to determine speed limits on state highways in Illinois?

The Illinois Department of Transportation (IDOT) holds the authority to determine speed limits on state highways in Illinois. This responsibility is part of their broader role in managing and improving the state's transportation infrastructure. IDOT conducts studies and assessments to ensure that speed limits align with safety data, traffic patterns, and road conditions. They utilize engineering principles and research to set these limits, which aim to protect public safety and enhance traffic flow.

The other entities listed do have roles within the broader context of transportation and public safety in Illinois. However, the Secretary of State primarily focuses on license and registration issues rather than highway management. The Department of Public Safety addresses law enforcement and emergency response rather than the establishment of traffic regulations. Local municipalities can set speed limits for roads within their jurisdiction, but this does not extend to state highways, which remain under IDOT's control. This division of responsibilities helps create a cohesive and uniform approach to traffic regulations across the state.