Three of four lanes have been closed on the M1 southbound between J17 and J16 near Daventry after the accident.
National Highways said almost four miles of traffic had stacked up by just after 5.30pm.
It tweeted: “#M1 southbound between J17 and J16 near #Daventry #Northampton. 3 lanes (of 4 lanes) are closed due to a collision.
“Delays building – almost 4 miles of congestion on the approach. Updates to follow soon.”
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