The history of public transport started in 1744, when the "Zeiserlwagen" (a kind of rack-wagon with seats) was mentioned first.
As
time went by these seats became more and more comfortable and these "omnibuses"
from latin omnibus - for all - became an important part of the cities transport
system. In October 1905 the "Vienna General Omnibus Compagnie" started
its service between Stephansplatz and Südbahnhof (southern railway station).
The city of Vienna started an provisional bus-service not before 1907, due to
the big success of the (electric) tramway. Even this line and another provisional
one were converted to tramway service and the buses were rebuild to lorries.
At least, in 1912, a regular bus service was started and tests for the best
bus construction started, but World War I stopped these ambitions. In the years
1928/29 the final breakthrough came with the putting into operation of 103 Fross-Büssing-buses
of type "W IV O". 
In 1936 the service with Diesel-buses started; the conversion
to right-hand traffic in 1938 took place without any problems as this option
was taken into consideration during the construction of these buses. During
WW 2 the services of buses was cutted back and in 1942 only line 20 went with
gas, which was carried in a one axle trailer. In 1943 the construction of a
trolley line between Währinger Gürtel and Sallmannsdorf started; because
of the war it went into service not before 1946. During this time bus-services
with trailers began and ended in 1961, three years after the end of the trolles-service.
During the 1950ies a lot of test took place, but in 1958 finally a standard
bus was found. In the years after more and more tramwaylines were replaced by
bus-lines and so new bus-garages have been built (Spetterbrücke and Raxstraße)
or former tramway garages have been rebuild (Grinzing). During this time (early
1960ies) the double-
decker
service started and lasted till 1991. For the lines in the city-center City-Busses
of Steyr came into service (1976-1995). In 1963 first experiments took place
to replace the gasoline with LPG (liquefied petroleum gas). In the same year
the first articulated buses went into service, from which more than 160 are
in service at the moment. 70 of them as low-floor vehicles
with 48 seats and a crush load of 144.
The biggest series of (standard) buses are the LU
200 M11, with MAN-Motors made by ÖAF Gräf & Stift and Steyr
from which 344 have been built between 1978 and 1992; but also these successful
buses are already completely replaced by their low-floor brothers, like NL
205. A smaller version of this bus is the NM 155
Midi-bus, from which 20 were in service, mainly in the city center
of Vienna, they already disappeared from Viennas streets. Due to the fact, that all buses of Wiener Linien (Vienna Lines) are
driven with LPG, Vienna has the most environmental friendly bus-fleet of all
cities in the world. Since August 2001 a new series of low floor buses are in
service. The type is NL 243 M12-LPG
and they have numbers from 8501 onwards. Starting in August 2001 a new gerneration of standard buses, named NL
243 M12-LPG with numbers starting at 8501, arrived. From March 2003
on articulated buses of type NG243 are in service. In 2005 followed new small
buses of type Kutsenits KB235; in November 2005 new two
door buses (MAN Lions City for LPG) with the designation NL
273T2 (nr. 8400) came into service. 2006 followed the three-door version NL273T3 which is also 2009 still in delivery. In june 2009 at UITP a Hybridbus was presented, maybe a little view to the future.
In October 2009 modern articulated buses of type NL273T4 follow, from which some 146 were ordered.