Driving in austria

Yes, get an IDP. Very easy from AAA and not expensive.

yes you do. And if you venture into Switzerland or Slovenia you will need a tax Vignette on the windscreen (or electronic but watch the gotchas); your car should be covered for Austria if it is Austrian registered.

If you go into France or Germany they each have different pollution programs so you will need a Crit'Air for France and a Umweltplakette in Germany if you are going into large towns or cities.

You will also need money in Austria for the high tolls on a couple of tunnels and highways and private roads not covered by the Austrian Vignette.

You will not need a vignette if you do not travel on the Austrian Autobahns. Even with the vignette you will pay additional tolls on the Autobahns like the Brenner Pass (as mentioned). Some places for short stretches on the Autobahn like near Kufstein and south from Bodensee you won't need one either. In winter in extreme cases, you might need snow chains in the higher elevations in the Alps.

The US Embassy in Vienna has excellent information on this topic on their website - https://at.usembassy.gov/motoring-driving-law/.

"A U.S. driver’s license alone is not sufficient to drive in Austria. The U.S. driver’s license must be accompanied by an international driver’s permit (obtainable in the U.S. from AAA) or by an official translation of the U.S. driver’s license, which can be obtained at one of the Austrian automobile clubs (ÖAMTC or ARBÖ ). This arrangement is only acceptable for the first six months of driving in Austria, after which all drivers must obtain an Austrian license."