Coordinates: 51°31′30″N 0°16′16″W / 51.525°N 0.271°W
Western Avenue is part of the A40, a major road running north-west out of London. Western Avenue is about 10 miles (16 km) long from its junction with Old Oak Common Lane in East Acton.
Construction began on Western Avenue in 1921. It was completed to Denham in 1943. At first, all intersections with other roads were on the ground.