The Almondsbury Interchange is the main junction for traffic to interchange between the M4 and M5. For the M4, it is Junction 20, and for the M5 it is Junction 15. The interchange is interlinked with M5 junction 16, which provides access to the A38.
The junction was the first example of a four-level stack in the country. Both motorways are dual two-lane plus hard shoulder through the interchange, though the approach roads are generally three lanes. The westbound M4 widens to 4 lanes on approach to the interchange. Link roads connecting from M4 to M5 pass over the top level of the interchange and links from the M5 to the M4 pass underneath all other levels.
The interchange opened in stages, with the M4 and M5 south to Junction 16 opening with the Severn Bridge in September 1966 and the M5 northwards in December 1971.
|SOUTH WALES, Cardiff|
|The MIDLANDS, Gloucester|
|The SOUTH WEST, Weston-s-Mare, Exeter|