The termscorduroy, corduroy bridge, andcorduroy road seem often to be used interchangeably by early writers to refer to a stretch of road made passable by a surface of transversely placed logs. The relatively late quotes for corduroy roadandcorduroy bridge(def. 2) suggest that a need for a distinction between them arose only when the latter term became widely used.
1792  (1911)  [It is certainly necessary to have a horse of the country to pass the bridges we everywhere met with, whether across creeks (very small rivers) or swamps.]
1824  Here . . . [is] the swamp, where there is enough of corduroy breeches [sic] . . . stump and rut paths, as any I have travelled in the province of the same length. . . .
1825  The honest farmer . . . has hitherto been compelled by want of snow, to plod his weary way over rough roads and corduroy bridges in his four-wheel wagon, instead of gliding smoothly to market in his sleigh.
1952  From there I . . . hobbled down a corduroy bridge made of uneven small, round peeled poles. . . .
2
a bridge having a surface of transversely placed logs.
1875  The stage rolled on across corduroy bridges, and through deep, gorgeously tinted woods.
1960  Bridges had to be built on the spot from available material and so on, from the corduroy road, the corduroy bridge was evolved. Of log construction, the bridges were also surfaced with unhewn logs.