The following highways are numbered 400:
Australia Murray Valley Highway
Canada Ontario Highway 400
Croatia D400 road
Cuba
Vía Monumental (2–400)
Ireland R400 road
Japan Japan National Route 400
Korea, South Capital Region Second Ring Expressway
South Africa R400 road in the Eastern Cape
Spain N-400 road
Turkey , a west–east state road in Turkey running from Datça, Muğla Province to Esendere at the Iranian border.
United Kingdom A400 road in London B400 road (Chancery Lane)
United States U.S. Route 400 Arkansas Highway 400 Florida State Road 400 Georgia State Route 400 Kentucky Route 400 Louisiana Highway 400 Maryland Route 400, a former state highway Nevada State Route 400 New York: New York State Route 400 County Route 400 (Erie County, New York) North Carolina Highway 400 Pennsylvania Route 400 (official designation for Pennsylvania Route 380) Puerto Rico Highway 400 South Carolina Highway 400 Tennessee State Route 400 Texas: Texas State Highway Spur 400 Farm to Market Road 400 Utah: Road 400 (Cottonwood Canyon Road) Virginia State Route 400 Virginia State Route 400 (former)