Yesterday I applied the left indicator as I approached my garage. I know to look in the side view mirror for aggressive Wiener drivers who can not be bothered to wait the 0.7 seconds for me to turn and will attempt to pass on the left. Sure enough. One crazyass Porsche owner tried to pass. Sigh. 
This sign tells drivers to keep a driveway free at all times. Even without such a sign, in a civilized society the need to keep a driveway free is inherent–driveway space is not special parking. 
But let us be civilized about the matter. Our U.S. home sits four houses from the elementary school, and there were countless occasions over the 16 years we lived there when I would arrive at home just as school ended, often to find a minivan blocking my driveway. No big deal. A simple wave to the driver, and the driveway was cleared. No harm, no foul. We are a civilized society in that respect.
There are times when I believe civilized society has taken a leave of absence here in Vienna. Let’s take this afternoon. The after school post-sports carpool pickup arrangement is finely tuned. Just past the roundabout for the 35A bus (from the school) is a quiet lane, but one that lacks a good deal of available parking, so my carpool friend and I time the pickup of our athletes wisely. 
I had carpool duty today. The athletes missed the expected bus. I was sitting in the MomMobile in front of a driveway, ever vigilant for its drivers. Oh! An elderly Viennese pea hen arrived and spent MINUTES sounding her horn for me to move from her driveway, LONG AFTER I had moved my vehicle.
She then stalked me, going in and out of her house to note my car tags no fewer than three times. At one point I felt I should alight from my vehicle to help her record the tags correctly, she seemed that troubled. 
The pea hen had come from the grocery store, where she had likely taken two parking spaces for herself. But. Details. 
Moments later, just as my carpool athletes arrived and tossed their gear into the wayback of the wagon, Pea Hen stormed out of her house to take note of my car tags once again. I hope my life is never so empty that I have time to sit in my living room window and stalk people.
I have a non-Austrian friend who recently moved from their cozy Döbling home to a different house here in the city. The reason? Their driveway was constantly blocked by restaurant-goers who considered the driveway to be a parking place, and the Polizei never acted on their complaints.
So, Frau Pea Hen, I do hope that the Polizei address your concerns in the same civilized fashion they did with those of my non-Austrian friend.