The year-long project will result in deliver extra lanes at M4 J15, improve local road access from the motorway and support the nearby New Eastern Villages housing development.
It is being funded by Highways England (£5m) with Swindon Borough Council (£4.8m), Swindon & Wiltshire Local Enterprise Partnership (£3m) and house-builders Persimmon and Redrow (£4.35m).
The upgrade follows the start of two major Swindon Borough Council schemes – the Wichelstowe underpass project further south near M4 junction 16, and improvement work at the White Hart junction, a link between the A419 and A420.
Main contractor MJ Church’s programme of work at J15 involves widening the A419 and A346 in the vicinity of the motorway.
Consulting engineer for the project is WSP.