via·duct /ˈvaɪəˌdʌkt/
  高架橋
  Vi·a·duct n.  A structure of considerable magnitude, usually with arches or supported on trestles, for carrying a road, as a railroad, high above the ground or water; a bridge; especially, one for crossing a valley or a gorge.  Cf. Trestlework.
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  viaduct
       n : bridge consisting of a series of arches supported by piers
           used to carry a road (or railroad) over a valley