a)to drive on Austrian highway you need to pay a fee (weekly, monthly or yearly) by buying the vignette, a sticker for your windscreen. The minimum is about 6 USD, if I remember well, and it is valid for a week. Also, the Tauern tunnel has a sustantial toll, but I can't remember the amount. b)speed limits are strictly enforced by police patrols with radar and laser guns, so stick to them, even if it's just a bare 80 kph on a deserted and boring highway stretch. You'll take a little more than the said 3 hours but you'll save some money.

To go into Slovenia you have to cross the Alps, so get ready for some mountain road driving on both sides.

Have a nice trip.

Paolo