Illinois' 139,000-mile network of state and local roads
is the third largest in the nation. The state also has the third
largest interstate highway system, including three of the nation's five
transcontinental routes that carry the most commercial vehicles.
IDOT is responsible for nearly 17,000 miles of roads.
The state also has 26,000 bridges, and IDOT is responsible for 8,000 of
them. Although IDOT is responsible for 12.5 percent of the total
highways and 30 percent of the bridges, those roads and bridges carry
two-thirds of the state's traffic.