This paper describes the development of a model called: "Dynamic Assignment in Time" which is meant as an instrument for Dynamic Traffic Management. The model can be used to give an insight in the short-term development (30-60 minutes) of traffic. The object for the final model is to correct the predictions with on-line data. The assignment method partitions the time of interest in periods. The traffic is represented by densities instead of the commonly used intensities. For each arc and each period the density is defined separately. The Origin-Destination (O-D) matrix is also defined separately for each period. The assignment is realized by calculating and assigning the shortest path for every O-D pair and each departure period. These shortest paths are based on arrival times in the nodes. The contribution of a traveller to the density on an arc in a certain period is determined by calculating the duration of presence on that arc in that period. In cases of overflow, the overflow is assigned to the preceding arc in the same period. Delays on arcs can be calculated with speed-densities functions. A dynamic All-Or-Nothing assignment can thus be executed. Because all other assignments are based on the iterative use of the All-Or-Nothing assignment, several assignments can be done. Currently the model is implemented on a Silicon Graphics workstation for evaluating and testing. (A)
Samenvatting