Just read on this is wiltshire.

M4 Westbound exit slip road closed due to serious accident, a motorcycle involved at J16 A3102 / B4005 (Swindon West). The accident happened at 19:30. The westbound exit slip road is closed, as it the eastern side of the J16 roundabout, between the eastbound entry slip road and the westbound exit slip road. No congestion on the main carriageway.