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|direction_b=East |terminus_b= at East Dubuque, IL |counties= |previous_type=US |previous_route=18 |next_type=IA |next_route=21 }} U.S. Highway 20 in Iowa is a major east–west artery which runs across the state, separating the northern third of Iowa from the southern two-thirds. It enters Iowa from Nebraska, concurrent with Interstate 129 and U.S Route 75, crossing the Missouri River at Sioux City. US 20 runs in a more-or-less straight line across Iowa, paralleling 42° 27' N. It leaves Iowa in Dubuque by crossing the Mississippi River into Illinois. The state of Iowa is in the process of upgrading US 20 into a four-lane, limited-access highway for its entire length in Iowa. ==Route description== U.S. Highway 20 enters Iowa concurrent with Interstate 129 and U.S. Route 75 on a freeway which bypasses Sioux City to the south and east. Immediately after crossing the Missouri River into Iowa, Interstate 129 ends and US 20/US 75 intersect Interstate 29 and US 75 Business. On the east side of Sioux City at Gordon Drive, US 20 exits the US 75 freeway, which continues towards Le Mars. East of Sioux City, U.S. Highway 20 continues as an expressway until Moville. From there, it is a rural, two-lane highway with only a short expressway segment just south of Holstein, that is briefly concurrent with U.S. Route 59. From US 59, it is about until US 20 has another four-lane segment, starting about one mile west of an interchange with U.S. Route 71 just north of Early. This final stretch of two-lane road will be upgraded to four-lane between 2016 and 2018.〔(【引用サイトリンク】title=Final Piece of US 20 Four-Lane Highway To Be Finished by 2018 )〕 From here until an interchange with Iowa Highway 4 northwest of Rockwell City, this is the newest section of 4-lane, which opened in November 2012. This new roadway passes to the north of Sac City and Lytton, and has another interchange with Iowa Highway 196 northeast of Sac City, but mostly has at-grade intersections, including County M54 into Sac City and N28 into Lytton. East of Iowa 4, and extending to the former beginning of the four-lane expressway northeast of Moorland (now an interchange with County D36), is a 4-lane section which opened in December 2010, and bypasses Rockwell City to the north. US 20 continues until just south of Highview, when it becomes a full interstate-standard freeway. The expressway south of Fort Dodge has interchanges with U.S. Route 169 and Webster County Route P59. East of Fort Dodge, US 20 overlaps with Iowa Highway 17 for , ending at Webster City. Near Williams, US 20 intersects Interstate 35. Beginning at the interchange with U.S. Route 65 is a section of four-lane freeway which, when completed, shaved nearly off of US 20's length. Prior to 2003, US 20 joined U.S. Route 65 north through Iowa Falls and then east towards Ackley and Parkersburg before heading south again to the freeway with Iowa Highway 14. The bridge crossing the Iowa River near Steamboat Rock is a ''launched steel I-girder'' bridge, the first of its kind in the United States. The bridge was designed to cross the old-growth woodland of the Iowa River valley with minimal impact. U.S. Highway 20 continues east towards Cedar Falls where it overlaps Iowa Highway 58 for just over . The western junction of Iowa 58 (Hudson Road) connects traffic to the University of Northern Iowa while the eastern junction of Iowa 58 is also the western junction of Iowa Highway 27, the Avenue of the Saints. Another mile east, in Waterloo, US 20 intersects U.S. Route 63 (Sergeant Road). On the southeast side of Waterloo, Interstate 380 joins US 20/IA 27 for before exiting with Iowa 27 south towards Cedar Rapids. U.S. 20 continues as a freeway east of Waterloo. It intersects Iowa Highway 150 at Independence and Iowa Highway 13 at Manchester, as well as junctioning a number of county roads serving smaller communities. Approximately between Independence and Manchester go over a terminal moraine and enter the Driftless Area, a region it will not exit until reaching Stockton, Illinois. At Delaware, US 20 changes from a freeway to an expressway with at-grade intersections; however, there are many interchanges where US 20 meets major roads, mostly at the villages and towns along US 20's route. US 20 serves Earlville, Dyersville (passing near the Field of Dreams filming site), Farley, Epworth, and Peosta before entering Dubuque. US 20 remains at least four lanes through Dubuque, but there are several stoplights along the route, particularly on the western edge of the city. There is a brief controlled-access section where the highway descends into the Mississippi River valley. Near the river, Locust Street connects US 20 with U.S. Highway 52, U.S. Highway 61, and U.S. Highway 151, which have entered the city from the south as an expressway and continue northward as a freeway. US 20 crosses from Iowa into Illinois via the Julien Dubuque Bridge. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「U.S. Route 20 in Iowa」の詳細全文を読む スポンサード リンク
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