Junction 8/9 near Maidenhead, Berkshire, and High Wycombe, Buckinghamshire is the only one in the UK with dual numbers. This arose at the time when the M4 turned north near junction 8, where it met the A308, and headed for the original junction 9, where the motorway ended at a roundabout interchange with the A4.
Upgrade of Junction 25, which is the main access point to Taunton and provides a critical link to the second strategic route into the South West via the A358 and A303.