Wiltshire Council has opened bidding for a motorway pinch point fix.
The project, set to start construction in 2027, will fully signalise, widen, and upgrade the junction to handle future traffic growth along the A350 corridor.
The upgrade will involve widening motorway bridges from two to three lanes, upgrading approaches, and removing nearby laybys.
Funding is secured through the Government's Major Road Network programme, with the scheme identified as a regional priority.
Wiltshire Council said the works will "maximise and optimise capacity of the junction within the bounds of the existing highway" and avoid piecemeal upgrades.
Author's summary: Bidding starts for £22m M4 upgrade.