Identification of parameters and verification of an urban traffic flow model. A case study in Wrocław

Abstract

A macroscopic model of road traffic flow in an entire city is constructed, using the example of Wrocław. The model is of deterministic-random type. The start and finish points of each vehicle journey are random elements of the model, while the street graph, routes of travel and traffic parameters are obtained in a deterministic manner. Vehicle speed is dependent on traffic density, and the time needed to cross an intersection depends on the number of waiting vehicles. The route of travel between given start and finish points is determined using Dijkstra’s algorithm, minimising the journey time. The street graph of Wrocław was constructed using data from the Open Street Map website. Identification of parameters and verification of the model were performed using hourly data on traffic volumes at the city’s major intersections in the years 2015–16, obtained from the Intelligent Transport System (ITS). Identification was made of the total number of vehicles travelling in the city at each time of day, a quantity that is difficult to determine by other methods. An accuracy of around 15% was obtained for times between 6.00 and 22.00, while for night-time the verification error exceeded 30%. The model may be used to analyse the impact of planned modifications to the transport system on traffic parameters in the city. It may also serve as a constituent of a larger model for investigating the effect of road transport on atmospheric pollution or for identifying areas at risk of noise pollution.