Seven-mile queues on M1 heading south from Milton Keynes and Northampton
Three lanes are closed near Dunstable following a smash involving a lorry and an overturned car.
Traffic is stalled from near junction 11 back beyond junction 12 for Flitwick with delays of up to 90 minutes above the usual travel time.
A spokesman for Highways England said at 7am: "Emergency services and traffic officers are in attendance following a collision involving multiple vehicles. We do not expect a return to normal traffic conditions until 10am."