Here are some pics of the most common means of public transportation in Vienna, the tram. There are about 30 lines all over Vienna.

[Linked Image from unet.univie.ac.at]

This is a type E1 car used on many lines, the oldest type still in service. The picture is taken in suburban Vienna.

[Linked Image from stud3.tuwien.ac.at]

This is a more recent E2 car in a very Viennese street.

[Linked Image from stud3.tuwien.ac.at]

And now the newest Ultra Low Floor (ULF) car.

Most lines are numbered, some have letters (as far as I remember D, J, N, O). Buses have a number followed by the letter A or B, A stands for municipial lines, B for private. Then we have 5 subway lines U1 to U6, U5 having been left out somewhere during the planning stage.
As far as I know all these vehicles operate on 750VDC, the buses are both Diesel and propane (I think).