Drivers have been told not to rely on their satnavs during work to repair a motorway hard shoulder this weekend.
National Highways said the westbound section of the M4 in Wiltshire, between junctions 16 and 17, will be shut on 14 November and 15 November as part of a £20million National Highways scheme.
It will be closed between 20:00 and 06:00 GMT, and two westbound lanes will also have 50mph speed restrictions until 17 February.
Chris Hilldrup, National Highways route manager, advised people to plan ahead and said: "We'd also urge people to adhere to the signed diversion routes and not follow their satnavs to potentially unsuitable roads."
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Why is the work taking place?
National Highways wants to stabilise 600 metres (1,968 ft) of the embankment alongside the M4 after a landslide.
Contractors MJ Church will move 25,000 tonnes of earth out of the way before they backfill with 19,500 tonnes of stone from a nearby quarry.
The work is part of a larger scheme between junctions 16 and 17 of the M4, which will also see the refurbishment of four bridges.
How will drivers be impacted?
The westbound carriageway between junctions 16 and 17 will be subject to overnight lane closures this weekend between 20:00 and 06:00 GMT.
Originally, the closures were planned for 12 to 13 November but were pushed back.
A signed diversion route will be in place via Chippenham.
How will HGV drivers be impacted?
During the two overnight closures, HGVs will be diverted westbound via the A3012, A4 and A350 to rejoin the M4 at junction 17, with the eastbound diversion in reverse.
When will things go back to normal?
The embankment work is due to be complete by 17 February which is when speed restrictions will lift.
At this point, National Highways said it will begin a project to restore four bridges and upgrade safety barriers on the M4.
This work is scheduled to run from autumn 2027 to spring 2028.
Why is the work needed?
Hilldrup, from National Highways, continued: "We appreciate roadworks can impact on people's journeys, and ahead of the weekend diversions, we advise people to plan ahead and allow extra time for their journeys.
"Once we have stabilised the embankment, we will refurbish the bridges and upgrade barriers to maintain the safety and reliability of this busy route for many years to come.
"Many of the roads and bridges we manage were built around 60 years ago and are nearing the end of their life span, so we're acting now and renewing them to prevent bigger problems further down the line."
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