The A45 near Wellingborough is partly closed because of a van fire.
The affected stretch road is the eastbound carriageway of the A45 between the A509 Wilby Way and A509 Turnells Mill Lane.
Traffic heading past Wellingborough towards Little Irchester is affected.
"Emergency services are at scene working to tackle the blaze," said a Highways England spokesman.
"Road users are advised to follow the 'solid circle' diversion symbol and exit the A45 eastbound at Wilby Way roundabout.
"Continue along the A509 until the A14 J9 interchange. At this interchange take the fourth exit off the roundabout onto the A14.
"Continue along the A14 toJ10. At the next interchange exit onto the A6 and continue along the A6 to re-join the A45 at the Chowns Mills roundabout."