605 ILCS 5/4-215
The Department may file with the governing body of any municipality or county a map of any territory within 1/2 mile on either or both sides of a State highway routing in which territory the Department believes subdivision development would have an effect upon an existing State highway or a future State highway the route of which has been adopted by the Department.
The clerk of the governing body of the municipality or county shall issue a receipt for the territorial map, and within 3 days after receiving such map, shall transmit to the Department one copy of each tentative map of any subdivision located wholly or partly within the territory outlined by the territorial map.
The Department, upon receiving a copy of the territorial map, may, within 15 days after receipt, make recommendations to the appropriate agency of the municipality or county in connection therewith regarding the effect of the proposed subdivision upon the State highway or State highway route.
605 ILCS 5/4-215