Modelling of vehicle traffic is one of the major challenges in the inventory of pollutant emissions from road transport. The diversity of conditions describing vehicle traffic entails a need for assumptions to be made, in order to enable data preparation. In the present paper we analyze the process of vehicle velocity to substantiate adoption of zero-dimensional characteristicsc of the process. In modelling of vehicle traffic it is, above all, the average value of velocity that is assumed to be a zero-dimensional characteristic of the velocity process. Additionally, vehicle traffic is assessed under driving conditions in urban and rural areas, as well as on highways and expressways. The paper presents the analysis of pollutant emissions from road transport in Poland, in the years 2000-2015, with reference to the type of driving patterns, which, in turn, depends on the dynamic characteristics of the velocity process.