Officers in Wiltshire say they've had reports of it happening between Junctions 19 and 15.
Wellington: Road Closure Information For Carnival
Somerset carnival season continues this weekend in Wellington with tens of thousands of people expected on the streets of the town.
Our Heart Angels will be there too taking your photos and putting them on the heart website.
It starts at 7.30 but road closures are being put in place earlier than that.
Exeter Road (from Perry Elm Roundabout to Bagley Road) 2pm to 11pm;
Exeter Road (from Bagley Road to Mantle Street) 6.45pm to 11pm;
Bagley Road 6.45pm to 11pm;
Popes Lane (from Blackdown Road to Exeter Road) 6.45pm to 11pm;
Mantle Street 6.45pm to 11pm;
High Street 6.45pm to 11pm;
South Street (from Bulford to town centre) 7.15pm to 11pm;
High Street 7.15pm to 11pm;
Taunton Road (B3187 to Chelston Roundabout) 7.15pm to 11pm;
Nynehead Road (from the unclassified Piccadilly road to Taunton Road) 7.15pm to 11pm.
CLICK HERE to read a history of the Carnival
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