Bus dispatching irregularity and travel time dispersion

Service reliability is one of the most important determinants for shifting people to public transport. In low-frequency services, the reliability is considered in terms of punctuality, which becomes significant also from the standpoint of operators, given that punctuality indicators are generally included in business models. As a support for further improvement in bus punctuality in the urban area of Rome, analyses were carried out using automatic vehicle location (AVL) data of a bus line with services mixed with other traffic components and therefore subject to high degrees of travel time variability. The analyses allowed the systematic components of bus dispatching irregularity to be revealed and to investigate to what extent these components are influenced by road congestion, and hence by delayed arrival times at terminals