speed limits to . As of July 24, 2014, the new signs are up on rural Idaho Interstates. On March 22, 2017, the speed limit on a four-lane, divided stretch of US 20 between Idaho Falls and Ashton was raised from to . Prior to the national reduction in January 1974 to , Idaho's speed limit was for interstates and on other highways. Illinois Interstate Highways in Illinois are usually posted with both minimum and maximum speed limits, except in some urban areas, particularly Chicago. The standard speed limit is 70 mph for rural freeways, a 45 mph minimum speed limit, 65 mph for other 4 lane divided highways, and 55 mph for all other highways. Urban freeway/interstate speed limits can range from as low as 45 mph in downtown Chicago, where all the major interstates merge, to as high as 70 mph in the outer portions of the Chicago and East St. Louis metro areas, and in some smaller cities. All the expressways leading directly out of downtown Chicago, which are The Dan Ryan Expressway, The Stevenson Expressway, The Eisenhower Expressway, and The Kennedy Expressway, have a 55 mph speed limit. Other expressways that branch off of the main ones leaving downtown, such as The Edens Expressway and The Bishop Ford Expressway, also carry a 55 mph limit. The Chicago Skyway does carry a 55 mph limit, but the tolled portion is signed at 45 mph. Lake Shore Drive carries a 40 mph speed limit from its northern terminus to E 31st Street, and from there to the end of the expressway, the speed limit is 45 mph. Some interstates in small cities (e.g. I-55/74 through Bloomington-Normal, I-39/90 through the Rockford area, I-57 through Champaign-Urbana) do not have reduced speed limits, and stretches of I-90 and I-355 in the Chicago suburbs are also signed at 70 mph. Most freeways and interstates in Cook, DuPage, and Lake Counties, and some interstates and freeways in Will County maintain a 55-60 mph speed limit. Due to the high population density, the only freeways in Cook County that exceed a speed limit of 60 mph are I-57 at the southern edge of the county, part of I-80 between Central Ave and Harlem Ave, I-90 west of Mt. Prospect Rd., and the southern segment of I-355, which passes through Cook County briefly before crossing into Will County to both the north and south. As