Estimating real-time urban traffic states in VISUM Online

In a road network there are a variety of detection devices to capture data on the traffic state. For example, each traffic-responsive signal system has been equipped with detectors, which at best may even transmit the acquired data to the control centre. Information which is not gathered automatically but manually, e.g. details on road works or congestion warnings transmitted by road users, constitutes another major data source. In the near future Floating Car Data, i.e. data recorded by moving vehicles and transmitted to the control centre, will gain importance. All these bits of information contribute to the description of the currently prevailing traffic states at different points of the road network. But they have to be combined in the appropriate way. A traffic model can be the suitable framework of such a data fusion since it allows a source-independent, abstract view of traffic in the road network concerned. The set of procedures implemented in VISUM Online solves the problem of deriving an estimation of the traffic state in a complete network on the basis of several locally distributed, individual measurement sites.