In railroads, the bed or foundation on which the superstructure (ties, rails, etc.) rests; in common roads, the whole material laid in place and ready for travel. [1913 Webster]

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OXFORD DICTIONARY

roadbed, n.
1 the foundation structure of a railway.
2 the material laid down to form a road.
3 US the part of a road on which vehicles travel.

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THESAURUS

roadbed

Autobahn, L, US highway, alley, alleyway, arterial, arterial highway, arterial street, artery, autoroute, autostrada, avenue, belt highway, blind alley, boulevard, branch, bypass, byway, cable railway, camino real, carriageway, causeway, causey, chaussee, circumferential, close, cog railway, corduroy road, county road, court, crescent, cul-de-sac, dead-end street, dike, dirt road, drive, driveway, el, electric railway, elevated, elevated railway, embankment, expressway, feeder, feeder line, freeway, gravel road, gravity-operated railway, highroad, highway, highways and byways, horse railway, interstate highway, junction, lane, light railroad, line, local road, main drag, main line, main road, metro, mews, monorail, motorway, parkway, pave, paved road, pike, place, plank road, primary highway, private road, rack railway, rack-and-pinion railway, rail, rail line, railroad, railway, right-of-way, ring road, road, roadway, route nationale, row, royal road, secondary road, sidetrack, siding, speedway, state highway, street, street railway, streetcar line, subway, superhighway, switchback, terminal, terminus, terrace, thoroughfare, through street, thruway, toll road, township road, track, tram, tramline, trestle, trolley line, trunk, trunk line, tube, turnout, turnpike, underground, wynd

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