It connects Dunkerque, a major ferry and container port at the northern end of the French coast with Aschaffenburg[1] on the north western tip of Bavaria.

Much of this has recently been resurfaced, but parts remain of subautoroute standard in terms of such details as junction lay-out and speed limits.

The passage of the E42 along the urban highway is marked by several sharp bends and, especially for westbound traffic, unavoidable lane changes as well as speed cameras.

The route follows no fewer than six different autoroutes in succession during its passage through southern Belgium (Wallonia), linking all its major cities, from the provincial capital Mons, to Charleroi and Namur, along with the major commercial and university city of Liège and its important cargo airport further to the east.

The final kilometers before the German frontier include towns and villages transferred from Germany to Belgium under the provisions of the 1919 Treaty of Versailles endorsed in 1925 by a referendum process not universally regarded as fair: over three quarters of a century later sign boards showing place names in French and German frequently have the French versions deleted by graffiti artists.