Motorists have been advised to find alternative routes after a serious accident forced officers to close part of the M1.
Northamptonshire Police closed the southbound M1 between junctions 16 and 15a after a lorry overturned, trapping the driver in the vehicle, at 6.20am today.
A police spokesman said the northbound carriageway was also closed temporarily to allow an air ambulance to land at the scene.
Emergency services worked to free the driver, the spokesman said, adding: "While that takes place, traffic is being taken off the carriageway at junction 16 and travelling either along the A45 into Northampton, around the ring road and back on to the M1 at junction 15a, or to the A5 heading south.
"As a result, these roads are extremely busy and motorists are being advised to either use alternative routes or to leave longer for their journey."