Traffic Flow Model (Coordination by PTV AG)

The term "Traffic Flow Model" as used in this context denotes a model that produces data about the movements of individual vehicles within their surroundings. In traffic engineering, such models are called "microscopic".

To fulfil the objectives of the project, traffic has to be modelled as movements of individual vehicles with a high time resolution. An existing and for a series of applications already proven model is chosen for this project: VISSIM. This model contains a psycho-physical car following model for longitudinal vehicle movements and a rule-based algorithm for lateral movements (lane changing). It is adapted to the requirements of this project.

VISSIM is a discrete, stochastic, time step based (0.1 - 1s) microscopic model, with driver-vehicle-units (DVU) as single entities. Since most parameters defining the driving behaviour, especially those for acceleration behaviour, are accessible from the graphical user interface, the overall driving behaviour is easy to modify in order to account for regional/local habits. The network model describes the infrastructure to be treated by the simulation model. It contains the coordinates of each street including curvature and gradient. Traffic rules, signals etc. are included explicitly. Available data (e.g. GIS or transportation planning software) can be used to a large extent. Traffic demand described by origin-destination (OD) matrices is input to the model. Routing algorithms to assign the traffic demand to the individual links are an integral part of it.