In the article the procedure of the reliability measures estimation for one route of the public transport network on the basis of a traffic flow modelling is suggested. A definition of UPTS reliability is based on the analysis of the Travel Time Reliability, Arrival Time Reliability and Probability of arriving to the stops with delay no more than m minutes. The approach is applied to the real task of the reliability estimation for Riga city public transport route. The microscopic model of transport network fragment is used for it.