605 ILCS 5/7-202.22

If the formula for the distribution of motor fuel tax funds, provided for in Section 8 of the "Motor Fuel Tax Law", approved March 25, 1929, as amended, is changed from that in effect on January 1, 1974, so that the percentage allocated for use in municipalities is increased, the amount of any such increase received by a municipality having 500,000 or more inhabitants shall be expended only for the construction, reconstruction, or improvement of unimproved or partially improved nonarterial residential streets.