Since 1992 Austria has been a member of the United Nations Framework Convention on Climate Change. It has also ratified the Kyoto-Protocol, which aims at limiting global warming to a maximum of 2 degrees ("2°C guard rail"). However, in the Kyoto period 2008 to 2010, Austria did not meet the prescribed greenhouse gas reduction by far. The main factor causing this failure was the economic sector "traffic". In the capital Vienna, 99% of this' sector's C02-emissions stem from road traffic.

This leads to the question how the overdue C02-reduction in road traffic can be achieved in spite of the predicted 25 % population growth in the city of Vienna from 2010 to 2050.

One quarter of all weekday trips are commuting trips. Therefore, commuting to and from work in Vienna can be taken as an example to research the "solution space" of urgent decarbonisation.

Decadic census offers transport mode-specific data on commuter relations within Vienna. The transport model of the city of Vienna is used as a representation of the street network while spatial data provided by the Statistik Austria is combined and edited in a GIS-System.

The combination of these three data-levels permits drawing conclusions concerning the causes behind mounting C02-output in Viennese commuter traffic from 1971 to 2001. A detailed look at residential areas, workplace locations and paths travelled in 2001 follows, with car-commuters being of special interest in this respect. Taking different points of view, settlement areas of particularly intense car-commuting are highlighted, together with a discussion of their local building densities.

A statistical analysis of spatial and traffic-related characteristics, retrieved from the data, brings forth factors that strongly influence the mileage of car-commuters. The knowledge of these factors furthermore sheds a light on the spatio-structural preconditions of settlement areas capable of minimizing C02-emissions.

Two scenarios then outline C02-reduction potential regarding commuter traffic for the year 2001. Concluding, a third scenario shows the implementation of the proposed solution - namely "densification"- in practice.

The results of this thesis clarify the impact of housing densities on travel behaviour and hereby highlight the issue of urban sprawl present within the city of Vienna. If the paradigm equating low housing density with a high quality of life would shift and traditional block perimeter was to be implemented again, the C02-neutral, "walkable" city would come within close reach once again.