Network Performance Degeneration in Dynamic Traffic Assignment : With Applications to Evacuation Modelling

EVAQ is a traffic model for ex-ante evaluations of evacuations plans. The model is still in development and it is uncertain whether EVAQ will accurately model network performance degeneration. At the same time it can be said that accurate network performance degeneration is very important for evacuations. The research of this thesis identifies that there are phenomena that contribute to network performance degeneration that are not modelled. Two important phenomena that are not included are the flow degeneration as soon as links become congested and the constraints that nodes (intersections) themselves have. Several general ideas were thought up to implement these phenomena. A selection was made on the basis of accuracy. Flow degeneration as soon as a link becomes congested has to do with the link model. The link model determines what number of vehicles can potentially enter and leave the link within a time step. In order to accurately determine these, the framework of Cell Based Queuing is developed. It represents the queue on a link as a set of cells that are related to successive time steps in the past. The theory of kinematic waves is applied which explains that in congestion the traffic states move upstream. Traffic states in the cells can thus be determined using the link outflow from the past. Link inflow is determined by the remaining storage capacity on the link. As an addition to the theory of kinetic waves, the cell at the end of the link is governed by saturation flow rather than kinematic waves. This implicitly applies a capacity drop. A newly developed node model evaluates constraints on the nodes. The new node model is a combination of these constraints and the constraints by link inflow that are already evaluated. The node model exists out of several sub models that are used for different node types. The controlled intersection model deals with combined use of conflict areas and the effect of green phases. The uncontrolled intersection model is based on a capacity formula that determines the capacity for a minor flow based on a major flow. The formula is used in a framework that relates all flows on the intersection. For roundabouts an existing model by Cetur (1986) is used. A similar framework is put in place to relate all flows over the roundabout. The model is adapted to work on lane level rather than link level for turbo roundabouts. For weaving sections, on-ramps and off-ramps a new model is developed that looks at lane specific demand. The new model needs more calculation time but produces more precise capacity estimations. Significant changes are found for the MFD and for queue lengths (spillback). The latter now resembles results from the Network Performance Degeneration in Dynamic Traffic Management microscopic model VISSIM quite closely and needs both the new link and node model. The new node and link model are part of the Dynamic Network Loading model of EVAQ. This model has been the centre of most changes performed for EVAQ and can be used in any other Dynamic Traffic Assignment model. Furthermore, the model is theory based and can thus be used for reversed engineering and more extensive analysis of bottlenecks, also for evacuation schemes.