Modeling meso network nodes

Vissim distinguishes meso network nodes and automatically generated meso nodes:

• You may exclusively define and edit meso network nodes (Mesoscopic node-edge model).

• You cannot define or edit meso nodes that were automatically generated by Vissim.

Comparable to nodes for dynamic assignment in microsimulation, meso network nodes must be defined where paths come together or significantly branch out.

For dynamic assignment with microsimulation, it is sufficient to use one node per real intersection. This node may contain multiple conflict areas that are independent from each other. These conflict areas only impact vehicles located precisely within their area.

In mesoscopic simulation, vehicles generally wait outside the meso network node due to conflict areas and then traverse the entire meso network node without stopping. This is why a meso network node must start at every position vehicles are meant to wait. If vehicles heading different turning directions are meant to stop at different positions of an intersection entry, you will need to create multiple separate meso network nodes. A single meso node for the entire intersection will not be sufficient.

In mesoscopic simulation you often need more meso network nodes to model intersections than nodes in dynamic assignment with microsimulation, even if the intersections are of similar complexity. This is particularly true when it comes to roundabouts, non-signalized intersections, intersections with bypasses, etc.

Each meso edge leading into a meso network node must be long enough to create a travel time on the node which is greater than the meso critical gaps of the conflict areas for the following turn relations. Otherwise, instead of the critical gap value defined, the travel time on the edge is used as the critical gap. Therefore it is necessary to define small meso network nodes and make sure the edges are sufficiently long enough. Follow the rules and examples given for defining meso network nodes (Rules and examples for defining meso network nodes).

Managed lanes routing decisions and dynamic routing decisions must not be defined within meso network nodes.