ZTL's

At least in Ortisei the areas you could not drive (ZTL) were very obvious and usually they actually had barriers preventing you from doing so which when an taxi or similar authorized car approached a barrier would automatically lower underground. It was actually very cool to see. I am not sure if there was a button somewhere the driver pushed or just sensed and lower for some cars or all cars but the roads I am referring to looked like pedestrian only roads so it was obvious to not drive on them.

As far as fears of accidentially driving through a ZTL in the Val Gardena area, you really should not have any.
If it looks like a pedestrian area and not a regular road don't drive down it.

All entrances to ZTL have the international road sign for "no motor vehicle access". It's a round circle that is white with a red border. Read below.
http://grandvoyageitaly.weebly.com/the-piazza/the-truth-about-ztl-zones-avoiding-tickets-in-italy

Pedestrian areas are more and more protected by automatic barriers which are called pilomats after this Italian company that makes them.

Don't try to go over them:
https://youtu.be/paHjgTDctVM

Thanks for the advice.

Richard