Overview
- An HGV collided with the M4 central reservation just after 02:11 on Thursday, October 1, damaging about 300 metres of barrier and spilling diesel across roughly 100 metres of the westbound carriageway.
- Wiltshire Police and National Highways led the response, reported no injuries, and had recovery teams on scene by mid‑morning while traffic officers began turning trapped vehicles from the rear.
- National Highways has fully closed the westbound carriageway between J16 (Swindon) and J17 (Chippenham) and shut lane 3 eastbound because of the vehicle’s final position.
- Drivers are being routed on signed Solid Diamond diversions with separate guidance for vehicles under and over 4.2 metres, sending smaller vehicles via Royal Wootton Bassett and the B4042 and larger vehicles via the A4 and A350.
- The closure is expected to remain for some time because diesel cleanup and barrier repair need specialist environmental and structural work, which will keep local roads through Royal Wootton Bassett, Brinkworth and Chippenham busier than usual.