The longest disruption on the motorway network will affect the M4 between junction 10 at Winnersh and junction 11 at Reading, which will close completely in both directions from 21:00 on Friday 18 September until 06:00 on Monday 21 September.
National Highways said the closure is required so Scottish and Southern Electricity Networks can install new high-voltage electricity lines across the motorway. Through traffic will be diverted via the A329(M) and B3270, with drivers advised to follow the signed route rather than satellite navigation.
A1 and A421 closed for the weekend
A second major weekend closure will affect freight movements between Bedfordshire and Cambridgeshire. The A1 northbound between Tempsford and Wyboston and the A421 eastbound between Renhold and Black Cat junction will both close from 21:00 on Friday until 05:00 on Monday.
National Highways said the shutdown is needed for drainage work associated with the £1 billion A428 Black Cat to Caxton Gibbet improvement scheme. A signed diversion will take traffic via the A603, A1 northbound, St Neots Road and A428.
The route is particularly important for freight because the A421/A428 corridor forms part of the connection between the M1 near Milton Keynes and the east coast ports of Harwich and Felixstowe. National Highways is building a new 10-mile dual carriageway between Black Cat and Caxton Gibbet, with most of the scheme currently scheduled to open in spring 2027.
The A1198 southbound at Caxton Gibbet will also close between 23:00 on Friday and 06:00 on Monday for street-lighting and drainage work.
M3 and Dartford Crossing restrictions
Further south, National Highways is also closing the M3 southbound between junctions 8 and 9 overnight as part of the M3 junction 9 improvement project. The works involve a traffic switch and vegetation clearance. National Highways lists southbound closures for 18 and 19 September and advises drivers to use the signed diversion.
Freight operators using the M25 should also be aware of weekend works at the Dartford Crossing. The Dartford west tunnel will close from 23:00 Friday until 06:00 Saturday, while the QEII Bridge will close from 21:00 Saturday until 09:00 Sunday. On Sunday night, the Dartford east tunnel will close, with no access for vehicles over 4.8 metres high.
National Highways warns that planned closures can change at short notice and recommends checking live traffic information before departure.
