Updating demand vectors using traffic counts on congested networks: a real case application

All the elements of a transportation system model generally suffer from some approximation. Normally the demand vector is considered the most crucial and problematic element to be simulated, and traffic counts are thus generally used to update it so that the whole model system is able to reproduce the observed link flows. Updating demand vectors using traffic counts has received considerable attention in recent years. In this paper the methodology proposed by Cascetta and Postorino (Fixed point models for the estimation of O-D matrices using traffic counts on congested networks. Transportation Science, Vol. 35, 2001) for updating the demand vector using traffic counts on congested networks is applied to a real case: the OD demand vectors for the city of Naples (Italy). The results show the good capacity of this methodology to reproduce the traffic counts measured. Furthermore, through the estimated OD vectors it was possible to make a structural analysis of transportation demand in Naples.