A-4 Skyhawk, an attack aircraft manufactured by Douglas Aircraft Company

V-2 rocket, as the actual model number for the German weapon

Audi A4, a brand of car

LNER Class A4, a class of steam locomotives, including the famous Mallard

A4 (Germany), a Bundesautobahn between Aachen and Görlitz, part of the E 40, which connects Calais and Ridder in Kazakhstan

The code for permission to use specific land or premises for pubs and bars in town and country planning in the UK

Curtiss Falcon an attack aircraft manufactured by Curtiss Aircraft Company

A4 road (England), connecting London to Avonmouth, Bristol

A4 (Netherlands), a motorway in the Netherlands connecting Amsterdam, The Hague and Rotterdam.

A4 road (Northern Ireland) in Northern Ireland

A4 autoroute (France), a highway connecting Paris to Strasbourg as part of the European routes E50 and E25

A4 (Poland), an incomplete road intended to connect Zgorzelec to Korczowa

HMS A4, an A-class submarine of the Royal Navy

USS Moccasin (SS-5), a Plunger-class submarine of the United States Navy

Ostautobahn in Austria

A4 (Switzerland), connecting Schaffhausen to central Switzerland

Southern Winds, the Argentine airline, as its IATA code

A440, the A above middle C

A4 (Croatia) in Croatia

The A4 Air Logistics branch of the UK Joint Force Air Component Headquarters

A4 (Romania), a planned motorway in Romania

Autovía A-4, is a Spanish autovía connecting Madrid to the Andalusia region.

Esk Highway, a state highway in Tasmania

A4 (Portugal), a highway connecting Amarante to Porto

A4 road (Luxembourg), in southern Luxembourg

A4 paper size, an international standard paper size (210×297 mm) defined by ISO 216