Dynamic Traffic Assignment Pack

Realistic time-dynamic assignment

For realistic modelling of congestion dynamics, OmniTRANS offers a macroscopic dynamic assignment model (MaDAM) that is faster, deterministic (no random effects) and easier to use than  microscopic simulation models.

State of the Art Propagation Model

MaDAM is suited to modelling policies for highway congestion that have coverage and impacts across metropolitan areas and regions linking several cities and towns. It has been designed to reflect the propagation of traffic through the network roads and junctions due to variation in demand over time and the response of traffic to dynamic conditions within the transport network.

The multi user class propagation model realistically simulates the accumulation and dissipation of queues on the road network, and the effects of queues extending upstream to block junctions.

Demand variation during the modelling period

The variation in demand throughout the modelled period can be represented in a number of ways. The dynamic assignment model can assign temporal profiles to the trip tables, which define the variation in the rate at which trips are released onto the network. Alternatively, a model of departure time choice can be used to allocate trips to each interval of the simulation based on the expected travel time for trips departing in each interval and information the effect arriving late or early would have on this choice.

Easy transition from Static to Dynamic Modelling

The Dynamic Highway modelling uses the same network as that for Static Assignment, so no new network structures need to be developed, making the transition very efficient and inexpensive. Some additional link attribute information is required, and this can be specified easily using the Project Setup facilities or the Link Attribute Editor. For very large networks, MaDAM can be used within a   cordon,  so  that only the  portion of the network of interest is modelled.

Model Output

The output of MaDAM can be viewed in OmniTRANS as a video display showing network characteristics changing with time. This can show changes in flow of traffic over time, or any other attribute such as speed and density, that varies during the simulation period.

The dynamic output can be used to identify the origin of congestionand queues in the network, providing invaluable insight into network behaviour. Often the cause of congestion is not near where it manifests itself.

Other outputs that can be generated by the model include dynamic skim matrices and data which shows how travel time along a user defined path (network segment) varies through time as traffic flows and congestion varies.

Feature diagram

The Dynamic Traffic Assignment Pack gives access to the following features:

Requirement

This pack requires the presence of the Data Manager and Static Traffic Assignment packs.