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Table 3 Main assumptions in and differences between the modelling methods
From: Modelling delay saving through pro-active incident management techniques
Context | Queue model | CTM-v simulation |
|---|---|---|
Time dynamics | Resolves only to the level of TIM phases, allowing different but constant arriving and capacity flows within each phase, with arrivals obtained by averaging 15-min profile values. | Discrete time model with 6 s time steps enabling not only detailed modelling of variations in capacity, demand and arriving flow over time, but also detailed modelling of changes in traffic dynamics. Demand is profiled with 15-min resolution. |
Space dynamics | Considers one homogeneous road section, or more precisely one incident site of unspecified size. The only spatial modelling is of queue extent. Off- and on-ramps are not modelled. | Divides the road section into cells in which the road characteristics may vary, enabling handling of exiting and entering traffic on off- and on-ramps. |
Traffic dynamics | Assumes that vehicle density changes instantly at each queue segment boundary (see Fig. 5).Neglects any delay due to reduced speed in traffic passing the incident or dispersing downstream. | Assumes that vehicle density is constant in each cell during each time step but can vary between cells and time steps. |