Long queues were formed on the M20 in Kent because of Brexit control tests at the Channel Tunnel.
Lorry drivers were left queuing while French authorities conducted tests for border checking procedures.
It comes ahead of the end of the Brexit transition period, scheduled for December 31.
Highways England said it had closed the entry and exit slip roads at Junction 11 today due to the number of HGVs parked on the hard shoulder.
It is understood the delays were caused by French authorities carrying out tests ahead of Brexit at the Eurotunnel terminal in Folkestone.
A spokesman for Getlink, which operates the Channel Tunnel, said: "The backlog (of traffic) built up this morning during tests conducted by the authorities in preparation for Brexit."
The spokesman said in the afternoon that traffic was now flowing "smoothly" through the terminal and services were operating as normal.
It is understood that further intermittent border tests will be carried out before the Brexit transition period ends.
Photographs showed dozens of freight lorries queued along the M20.
Highways England tweeted: "M20 coastbound at J11 Westenhanger - the entry slip is now closed due to heavy congestion in the area due to delays at Eurotunnel.
"Due to the heavy congestion with HGV's at this location, for safety reasons we have also closed the exit slip at J11 Westenhanger due to the amount of lorry's parking up along the hard shoulder all the way back to exit slip."
The Channel Tunnel connects Folkestone to Coquelles near Calais in France.
It comes as MPs supported curbs to post-Brexit powers relating to international legal agreements.
And Chancellor Rishi Sunak said he was determined that the United Kingdom would remain a global leader for asset management after Brexit.
"We're beginning a new relationship with the EU," Sunak said in comments to a conference organised by The Investment Association, an industry group.
"And as we do so, we are determined that the UK will remain a global leader for asset management," he added.
