605 ILCS 5/3-102
In accordance with the provisions of such Federal Aid Road Act, as soon as the State has made provision for the completion and maintenance of 90% of the network or primary or interstate and secondary or intercounty federal aid highways equal to 7% of the total public highway mileage of the State specified in the Federal Aid Road Act, the Department may, with the approval of the designated authority of the United States Government, increase the mileage of such primary or interstate and secondary or intercounty network by additional mileage equal to not more than 1% of the total public highway mileage of the State, and thereafter may make like increases in the mileage of such network whenever provision has been made for the completion and maintenance of 90% of the mileage of such network previously authorized in accordance herewith, and may construct and improve highways so selected in accordance with this Code and any other laws applicable, as moneys are appropriated for this purpose and made available by Acts of Congress and Acts of this State.
When selecting highways to be added to such network by and with the approval of the designated authority of the United States Government, as heretofore provided, the Department shall, so far as is practicable and consistent with the Acts of Congress, distribute in the several counties the mileage proposed to be added, and, as nearly as may be, so as to provide simultaneously for additional highways in the different sections of this State.
When designating the projects on such network of highways which are to be improved with the current allotments of federal funds made available by Acts of Congress and with funds made available by Acts of this State to be used with such federal funds, the Department shall distribute such federal aid projects equitably and fairly among the different sections of the State and, so far as is practicable and consistent with Acts of Congress, among the several counties.
605 ILCS 5/3-102