If you are thinking of visiting this area of Belgium or Northern France why not consider stopping en route to see some of the numerous monuments and memorials. Many of them are easily reached via the autoroutes.
Arras, Amiens and Ieper are more than interesting in their own right and worthy of a full day whilst numerous others would merit at least the lunch stop and a potter round.
If you are on your way to places further afield consider the fact there is every chance that somebody in your family was involved in the Great War - why not take a few hours out and make a pause to honour their memory.

Map: Ieper | Map: The Somme | Map: Chemin des Dames | Map: Verdun
Map: Arras | Map: Cambrai | Map: Lens/Loos | Map: Soissons
Map: Belleau Wood | Map: Fromelles | Map: Villers-Bretonneux
It is not possible to show every road and town. The above links all provide more detailed views.