R4, R04, R.4, R-4, or R/4 may refer to: Military Aircraft Caudron R.4, World War I French reconnaissance aircraft, first flown in 1915 Curtiss R-4, air ambulance version of the American Curtiss Model R utility aircraft, first flown in 1915 Sikorsky R-4, American helicopter, first flown in 1942 Ships , Royal Canadian Navy destroyer , U.S. Navy submarine Weapons R4 assault rifle, produced by South African manufacturer Vektor R4 carbine, assault rifle used by the Philippine Marine Corps Bisnovat R-4, Soviet missile Other military Plan R 4, the World War II British plan for an invasion of the neutral state of Norway in April 1940 Science R4, designation of risk phrase "Forms very sensitive explosive metallic compounds" R4 nuclear reactor, the fourth nuclear reactor built in Sweden Exotic R4, in mathematics, a differentiable manifold Transportation Cars R4, abbreviation for rear-engine, four-wheel drive layout R4, a sub-class of Group R rally cars Jaguar R4, Jaguar Racing's car for the 2003 Formula One season McRae R4, a rally car designed in part by Colin McRae Renault R4, alternative name for the Renault 4 Suzuki GSX-R/4, a concept car made by Suzuki in 2001 Roads R4 ring road in Ghent, Belgium R4 expressway (Czech Republic) R4 expressway (Slovakia) R-4 motorway (Spain) Radial Road 4 or R-4, an arterial road of Manila, Philippines Other transportation R4 (Canberra), a bus route in Canberra, Australia R4 (New York City Subway car) R4 (Rodalies de Catalunya), a commuter rail line in Barcelona, Catalonia, Spain R4 41st Avenue RapidBus, an express bus service in Vancouver, BC, Canada Video games R4: Ridge Racer Type 4, a racing game for Sony PlayStation, developed by Namco Rush Rush Rally Racing, a racing game for Sega Dreamcast, developed by Senile Team R4 cartridge, a Nintendo DS flash cartridge Other uses BBC Radio 4 the premier BBC speech radio station R4, a building in the Norwegian Government quarter (Norw. Regjeringskvartalet) Region 4, the DVD region code for most of Mexico, Central America, South America, Australia, New Zealand, Oceania See also 4R (disambiguation)