This paper presents the research and analysis process showing that transport system customers have a specific perception of service quality, as an indicator of transport system. Determining satisfactory level of service quality implies knowledge of travel demand and travel behaviour. There are a lot of elements that define the transport system quality. The goal of this paper is to identify the public transport system’s service quality elements that should be primarily acted on, in order to increase the level of service quality from transport system users’ (public transport users’ and non-users’) point of view, with minimal investment. The paper describes a specifically defined research methodology for determining service quality elements that should be primarily acted on, from the transport system users’ point of view. Methodology involves the use of Importance Performance Analysis (IPA) which is upgraded with the state preferences analysis. Presented methodology, which is used to determine user perception of service quality, can be considered to be universal. This methodology can be applied in other cities, with additional research that must precede its use. The methodology was tested on transport system users in Belgrade.

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It is generally know that adverse weather conditions cause changes in urban transportation system. Research of weather impact on the urban transportation system was additionally intensified by actualisation of climate changes problem. In urban area, precipitation may reduce the efficiency of transportation systems, since it often results in larger travel times and higher congestion levels in street networks. Therefore, it is important to examine the impact of precipitation on the urban street capacity. In accordance with climate characteristics of research area, the focus of this paper was on the rain impact. Impact of rain was analysed only in the context of transport supply, and not of transport demand. Sensitivity of the street network capacity was chosen to represent transportation system supply. It was analysed through the changes in saturation flow rate under the rain. Results of the research have shown significant sensitivity of street network capacity on the rain impact. Moreover, the rain impact was quantified by the capacity sensitivity coefficients, which were implemented in procedure of capacity calculation.

The importance of transportation modeling, especially personal car flow modeling, is well recognized in transportation planning. Modern software tools give the possibility of generating many development scenarios of transport system, which can be tested quickly. Transportation models represent a good (and necessary) basis in the procedure of environmental traffic impacts and energy emission estimation. Research in this paper deals with the possibility of using transportation modeling as a tool for estimation of some air pollution and global warming indicators on street network, produced by personal cars with internal combustion engines. These indicators could be the basis for defining planning and management solutions for transport system with respect to their environmental impacts. All the analyses are based on several years of research experience in Belgrade. According to the emissions of gases from the model, the values of other green house gases can be estimated using the known relations between the pollutants. There is a possibility that all these data can be used to calculate the transportation systems impact on temperature increase in urban areas.