The M1 is gridlocked heading towards Northampton ahead of Wednesday's morning rush hour following a lorry fire.
Three out of four lanes are blocked southbound near junction 16 with National Highways warning of queues back to junction 19 and delays up to an hour by 7.30am.
A spokesman for the agency said: "There are long delays of at least 60 minutes above usual journey times between junctions 17 for the M45 and 16 at Northampton due to this ongoing vehicle fire.
"Northamptonshire Fire and Rescue Service are on scene and are working to extinguish the fire but queues approaching the scene are approximately seven miles in total back to the M6.
If this lane closure impacts on your planned route, please allow extra journey time. Plan ahead, you may wish to re-route or even delay your journey."
Sensors also showed the A5 getting busy as drivers attempt to avoid the motorway queues.