Drivers were urged to avoid the A14 in Northamptonshire after heavy snow fell in the county overnight.
Police said there had been "multiple collisions" on the road between junctions 1 and 3 near Kettering, with queues stretching back 13 miles, while a number of broken down HGVs also caused problems.
Some motorists reported on social media being stuck in traffic for more than seven hours.
Police warned people to avoid the road if possible, while 4x4 vehicles were sent to check on the welfare of people in stationary traffic.
The road finally reopened in both directions in the early afternoon, although traffic was still moving very slowly.
Elsewhere, flights at Stansted Airport were temporarily suspended for a time on Wednesday morning while snow was cleared from the runway, but it has now reopened.
Both Stansted and Luton Airports are telling passengers to check with their airlines before setting off, as well as allowing extra time to get to the airport.
Ryanair have confirmed 16 flights have been cancelled at Stansted due to the weather conditions.
"Due to adverse weather conditions, the runway was temporarily closed for snow clearance and has now reopened," a Stansted spokesperson said.
“Incoming and departing flights have been disrupted, with some flights cancelled.
“Passengers are advised to check the status of their flight with the airline before travelling to the airport. Passengers whose flights are cancelled should not travel to the airport before checking with their airline.”