625 ILCS 5/11-604
2021 Illinois Compiled Statutes|Chapter 625 - VEHICLES|625 ILCS 5/ - Illinois Vehicle Code.|Chapter 11 - Rules Of The Road

 (from Ch. 95 1/2, par. 11-604)Sec. 11-604. Alteration of limits by local authorities.(a) Subject to  the limitations set forth in this Section, the county board of a county  may establish absolute maximum speed limits on all county highways,  township roads and district roads as defined in the Illinois Highway  Code, except those under the jurisdiction  of the Department or of the Illinois State Toll Highway Authority, as  described in Sections 11-602 and 11-603 of this Chapter; and any park  district, city, village, or incorporated town may establish absolute  maximum speed limits on all streets which are within its corporate  limits and which are not under the jurisdiction of the Department or of  such Authority, and for which the county or a highway commissioner of  such county does not have maintenance responsibility.(b) Whenever any such park district, city, village, or  incorporated town determines, upon  the basis of an engineering or traffic investigation concerning a  highway or street on which it is authorized by this Section to establish  speed limits, that a maximum speed limit prescribed in Section 11-601 of  this Chapter is greater or less than is reasonable or safe with respect  to the conditions found to exist at any place or along any part or zone  of such highway or street, the local authority or park district shall  determine and declare by ordinance a reasonable and safe absolute  maximum speed limit at such place or along such part or zone,  which:(1) Decreases the limit within an urban district, but     not to less than 20 miles per hour; or(2) Increases the limit within an urban district, but     not to more than 55 miles per hour; or(3) Decreases the limit outside of an urban district,     but not to less than 35 miles per hour, except as otherwise provided in subparagraph 4 of this paragraph; or(4) Decreases the limit within a residence district,     but not to less than 25 miles per hour, except as otherwise provided in subparagraph 1 of this paragraph.The park district, city, village, or incorporated  town may make such limit applicable  at all times or only during certain specified times.  Not more than 6  such alterations shall be made per mile along a highway or street; and  the difference in limit between adjacent altered speed zones shall not  be more than 10 miles per hour.A limit so determined and declared by a park district, city, village,  or incorporated town becomes effective, and suspends the application of  the limit prescribed in Section 11-601 of this Chapter, when appropriate  signs giving notice of the limit are erected at the proper place or  along the proper part or zone of the highway or street.  Electronic  speed-detecting devices shall not be used within 500 feet beyond any  such sign in the direction of travel; if so used in violation of this  Section evidence obtained thereby shall be inadmissible in any  prosecution for speeding.  However, nothing in this Section prohibits  the use of such electronic speed-detecting devices within 500 feet of a  sign within a special school speed zone indicating such zone, conforming  to the requirements of Section 11-605 of this Act, nor shall evidence  obtained thereby be inadmissible in any prosecution for speeding  provided the use of such device shall apply only to the enforcement of  the speed limit in such special school speed zone.(c) A county engineer or  superintendent of highways may submit to the Department for approval, a  county policy for establishing altered speed zones on township and county  highways based upon engineering and traffic investigations.(d) Whenever the county board of a county determines that a maximum speed limit  is greater or less than is  reasonable or safe with respect to the conditions found to exist at any place  or along any part or zone of the highway or road, the county board shall  determine and declare by ordinance a reasonable and safe absolute maximum speed  limit at that place or along that part or zone.  However, the maximum speed  limit shall not exceed 55 miles per hour. Upon receipt of an engineering study for the part or zone of highway in question from the county engineer, and notwithstanding any other provision of law, the county board of a county may determine and declare by ordinance a reduction in the maximum speed limit  at any place  or along any part or zone of a county highway whenever the county board, in its sole discretion, determines that the reduction in the maximum speed limit is reasonable and safe.  The county board may post signs designating the new speed limit. The limit becomes effective, and suspends the application of the  limit  prescribed in Section 11-601 of this Chapter, when appropriate signs  giving notice of the limit are erected at the proper place or along the  proper part of the zone of the highway.  Electronic speed-detecting  devices shall not be used within 500 feet beyond any such sign in the  direction of travel; if so used in violation of this Section, evidence  obtained thereby shall be inadmissible in any prosecution for speeding.  However, nothing in this Section prohibits the use of such electronic  speed-detecting devices within 500 feet of a sign within a special  school speed zone indicating such zone, conforming to the requirements  of Section 11-605 of this Act, nor shall evidence obtained thereby be  inadmissible in any prosecution for speeding provided the use of such  device shall apply only to the enforcement of the speed limit in such  special school speed zone.  (Source: P.A. 95-574, eff. 6-1-08; 95-788, eff. 8-7-08.)