I know this thread is specifically about blocking driveways, I just wanted to add something about blocking parked cars.
On days of alternate side parking one side of the street has to be completely cleared for approx 2 hours. Officially its illegal to double park on the other side. However, for those 2 hours its overlooked and u will not be ticketed.
Very often I see people who want to drive off, but they CANT because they are parked next to the curb, and they are blocked by a double parked car.
Please practice some mentchlechkeit. If u will temporarily double park your car due to alternate side parking, and your blocking in another car, leave a telephone number on your car where u can be reached so that u can move your car if necessary.