M4 | Wiltshire | Carriageway Closure | Expect Delays

Incident timeline

1. 02:59, 15 AugFirst report

   The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

2. 03:06, 15 AugUpdate

   The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

3. 03:41, 15 AugUpdate

   ⏱ Still active — no changes from National Highways. Incident ongoing for 41 minutes. Monitoring continues.

4. 03:46, 15 AugUpdate

   The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

5. 04:16, 15 AugUpdate

   ⏱ Still active — no changes from National Highways. Incident ongoing for 1h 16m. Monitoring continues.

6. 04:21, 15 AugUpdate

   The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

7. 04:51, 15 AugUpdate

   ⏱ Still active — no changes from National Highways. Incident ongoing for 1h 51m. Monitoring continues.

8. 04:56, 15 AugUpdate

   The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

9. 05:26, 15 AugUpdate

   ⏱ Still active — no changes from National Highways. Incident ongoing for 2h 26m. Monitoring continues.

10. 05:31, 15 AugUpdate

    The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

11. 06:01, 15 AugUpdate

    ⏱ Still active — no changes from National Highways. Incident ongoing for 3h 1m. Monitoring continues.

12. 06:06, 15 AugUpdate

    The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

13. 06:36, 15 AugUpdate

    ⏱ Still active — no changes from National Highways. Incident ongoing for 3h 36m. Monitoring continues.

14. 06:41, 15 AugUpdate

    The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

15. 07:11, 15 AugUpdate

    ⏱ Still active — no changes from National Highways. Incident ongoing for 4h 11m. Monitoring continues.

16. 07:16, 15 AugUpdate

    The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

17. 07:21, 15 AugUpdate

    ✅ Incident cleared — M4 reopened at 07:21 on 15 Aug 2026. Total disruption: 4h 21m. All lanes open, traffic returning to normal.

18. 16:55, 6 NovFinal update

    The M4 westbound in Wiltshire is closed between J16 (near Swindon) and J17 (near Chippenham) following a serious collision that occurred approx. 02:06 on the 15.08.26

Wording from National Highways, recorded as it changed.

More on the M4

• M4M4 - IncidentMinor · 7h ago
• M4M4 - IncidentMinor · 7h ago
• M4M4 - IncidentMinor · 7h ago
• M4M4 - IncidentSevere · 10h ago
• M4M4 - IncidentModerate · 10h ago