The Brexit will start possibly on 31/10/19 at 00h
This can cause large traffic problems on the important belgian connecting roads (A11, N31, E40) but also on some secondary roads.
The region of Bruges/Zeebrugge, West coast, and Menen will probabely be most affected.
In France, the region of the ports of Dunkerque, Calais, Le Havre, Cherbourg,... will also have traffic nuisance.