R4
R4, R04, R.4, R-4, or R/4 may refer to:
R4 (New York City Subway car)
R4: Ridge Racer Type 4, a racing game for Sony PlayStation, developed by Namco
R4 (Rodalies de Catalunya), a commuter rail line in Barcelona, Catalonia, Spain
Rush Rush Rally Racing, a racing game for Sega Dreamcast, developed by Senile Team
Plan R 4, the World War II British plan for an invasion of the neutral state of Norway in April 1940
R4DS, a Nintendo DS storage device
Region 4, the DVD region code for most of Mexico, Central America, South America, Australia, New Zealand, Oceania
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
Cars
R4, abbreviation for rear-engine, four-wheel drive layout
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
