Updated: 28 August 2026, 10:20 BST
This article has been updated following new information from National Highways. The road authority has now published the first confirmed September closure dates for the St Georges Bridge repair scheme near junction 21 at Weston-super-Mare.
From 10pm on 3 September, a 50mph speed limit and average-speed cameras will be introduced around the works. Narrow lanes and hard-shoulder running will follow later in the month.
The first full motorway closure is scheduled for 18–20 September, when the M5 northbound will close overnight between junction 22 and junction 20, from 10pm until 6am.
Traffic will be diverted from junction 22 via the A370, A38 and A4 Bristol Portway, rejoining the M5 at junction 18.
A second major closure will follow from 25–27 September, when the M5 southbound will close overnight between junction 19 and junction 22, again between 10pm and 6am.
The signed southbound diversion will take traffic via junction 18, the A4 Bristol Portway, A38 and A370, before rejoining the motorway at junction 22.
National Highways says three narrow northbound lanes will operate continuously from 19 September, while three narrow southbound lanes will be introduced from 24 September.
Weeknight lane closures are also scheduled throughout much of September.
Wider traffic order runs until 2029
The September works sit within a much broader statutory traffic order covering the M5 between junction 19 at Portishead and junction 22 at Burnham-on-Sea.
The order comes into force on 30 August, with works expected to start on or after 1 September as part of bridge and parapet refurbishment.
It authorises overnight closures between 8pm and 6am, including the northbound M5 between junctions 22 and 20 and the southbound carriageway between junctions 19 and 22.
Individual entry and exit slips at junctions 19, 20, 21 and 22 can also be closed, along with access associated with Sedgemoor services.
At junction 21, some southbound exit and northbound entry slip-road closures can remain in place for an entire weekend, from 8pm on Friday until 6am on Monday.
The restrictions will not all apply continuously. The order instead gives National Highways the legal power to introduce individual closures and restrictions when required as the works progress.
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Width restrictions could affect HGVs
The order also allows vehicles wider than 2 metres to be prohibited from using specified motorway lanes while temporary traffic management is in place.
As most HGVs exceed this width, the measure could effectively confine lorries to the inside lane on affected stretches.
A temporary 50 mph speed limit, contraflow arrangements and hard-shoulder running can also be introduced during different stages of the works.
The statutory order is due to remain available until 20 December 2029, indicating that disruption associated with the wider refurbishment programme could continue intermittently for more than three years.
