The A4 is a major road in England from Central London to Avonmouth via Heathrow Airport, Reading, Bath and Bristol. It is historically known as the Bath Road with newer sections including the Great West Road and Portway. The road was once the main route from London to Bath and the west of England and formed, after the A40, the second main western artery from London. Much of the route is now paralleled by the M4 motorway, which carries the bulk of long distance traffic in this corridor, leaving the A4 primarily for local traffic, though sections in London and Bristol particularly are still major through routes.