Traffic is crawling for around 12 miles on the M1 southbound from Northampton to Milton Keynes following a crash on Tuesday morning (November 2).
National Highways sensors show tailbacks from near to Newport Pagnell Services all the way back to junction 15A at just after 9pm.
Reports say three cars and a van have been involved in a collision.
A spokesman confirmed one lane is blocked and it is disruption could continue until early-afternoon.
The A5 is also busy between Towcester and Milton Keynes as drivers attempt to avoid motorway queues.