You don't say where you're starting from, or where you're going to, but assuming a channel port and Italian lakes area, the route we would use is E25 from Dunkirk via Lille,Namur, Luxembourg then A13, A8 towards Saarbrucken, short single carriageway from Pirmasens to Landau, A65, then A8 towards Ulm, then A7 to Kempten and single carriageway to Austrian border and over Fern Pass (easy), head towards Imst avoiding motorway and follow that road over the Reschen pass (easy) into Italy ending up near Bolzano. The Austrian motorway charges are much cheaper than the Swiss vignettes, but there's also a toll on the Brenner. If you're going a long way south in Italy, it's probably worth paying the tolls unless you've got lots of time on your hands.
John M