The paper describes the urban passenger transport system which is a set of interdependent subsystems: «city», «transport», «passengers». The urban passenger transport performance indicators have been determined for all system participants. The objective functions of an optimization problem of urban passenger transport are given in general terms. The optimization criterion for traffic routing of urban passenger transport has been determined, which takes account of mutual influence of the interests of all system participants has been determined. The passenger traffic flow density on the studying road section, has been suggested as such optimization criterion. The formulation of an optimization problem of urban passenger transport have been defined as well.