This master thesis is the final assignment within my master program at the Royal Institute of Technology in Stockholm. The thesis is performed in cooperation with WSP and linked to their research project ‘On the right track”. The aim of this master thesis is to identify and estimate the impacts resulting from future passenger transports in Mälardalen region by using a scenario study methodology. The research problem this thesis is dealing with is the negative societal consequences can be expected to increase as a result of the predicted rise in passenger traffic volumes in Mälardalen. Four alternative scenarios are introduced in the thesis and compared with the projected development; Scenario 1 assumes more energy efficient vehicles, Scenario 2 expects an extended fuel substitution, Scenario 3 is based on a doubling of the public transport travelling and Scenario 4 assumes that the structurally enforced travels will be halved. From a methodological perspective, the results and discussion in the thesis indicate firstly that Mälardalen is a suitable geographical boundary in future studies related to the transport system as the region is becoming more integrated and secondly, that a wide range of impacts and modes of transport must be considered when sustainable transports are discussed. The results of the scenario analysis can be summarized as if the projected passenger transport development will decrease the energy use and the emissions, despite longer travel distances, as a result of more energy efficient vehicles. In order to reduce the negative impacts of passenger transports further, the most favorable development paths to follow are to either decrease the structurally enforced trips or to increase the public transit travelling. The reason why neither the projected development nor Scenario 1 and 2 will reduce the negative impacts is that such developments cannot reduce consequences that are not related to energy or fuel use to the same extent.