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Hogg's Hollow Bridge, originally known as the Yonge Boulevard Viaduct, is a set of four separate highway bridges that span the Don River Valley in Toronto, Ontario, Canada, and carries 14 lanes of Highway 401. The four structures are the busiest multi-span bridge crossing in North America, surpassing the Brooklyn Bridge. == Description == The Hogg's Hollow Bridge has a 14-lane cross section: 6 collector lanes, 8 express lanes. The road surface and bridge decks require constant maintenance due to the wear and tear from high traffic volumes. Since 2001, an Ontario tall-wall concrete barrier has replaced the steel guide–rail in the median separating eastbound and westbound traffic. The late 1960s conventional truss lights have been replaced by high-mast lighting. Starting from 2002, the westbound collector lanes on the outer north bridge have also undergone rehabilitation (replacing road surface, guard rails and/or concrete barriers). The westbound collector traffic has been rehabilitated; the project included the north side outer bridge and the Yonge Street overpass. Additional high mast lighting was added in late 2009. From 2006 to 2008, the eastbound collector lanes were rebuilt and the reconstruction stretched from east of Avenue Road all the way to Bayview Avenue, encompassing the south side outer bridge and Yonge Street overpass. This did not include the on–ramp junction with Lord Seaton Road. The inner eastbound express lanes will be next on the reconstruction process. Once completed, the entire bridge will use the Ontario tall-wall barrier system. Due to land constraints of the Valley and the need to accommodate the bridges, the adjacent interchange with Yonge Street is of a modified Parclo design instead of the typical Parclo A4 configuration used on most Ontario freeway junctions. The interchange is also one of the narrower points of Highway 401's collector-express system, not just because of the bridges but also because of the suburbs east of Yonge Street (which forced the province to expropriate land in order to expand that segment of Highway 401). Although there are a total of 14 lanes of traffic on the four bridges, there are only 12 through lanes that cross Yonge Street, as the off–ramps and on–ramps default onto the main lanes instead of being additional deceleration and acceleration lanes. At the foot of the bridges is the Earl Bales Park and Ski Centre in the north and Don Valley Golf Course to the south, both owned by the City of Toronto. An access road branches off from the westbound on–ramp and travels downward to the valley below and ends in a cul-de-sac just south of the eastbound collector lanes. It is closed to regular vehicular traffic and used by Ontario Ministry of Transportation maintenance crews (and their contractors) as well as housing the Macdonald-Cartier Emergency Service building of the Toronto Transit Commission used for both emergency access to/from track level of the subway but also as an access point for maintenance crews. The bridges can be clearly seen from Yonge Street looking northwest and north of York Mills Road and Wilson Avenue. 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「Hogg's Hollow Bridge」の詳細全文を読む スポンサード リンク
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