Modeling meso network nodes

In addition to created or manually defined meso network nodes, there are meso nodes that are automatically generated with the meso graph.

• Only those meso network nodes that you create for the entire Vissim network or define individually in the Network editor can be edited (Mesoscopic node-edge model).

• The meso network nodes generated by Vissim when creating the meso graph cannot be defined or edited.

Placement within the Vissim network

Comparable to nodes for dynamic assignment in microsimulation, meso network nodes must be defined where paths come together or significantly branch out. These and all other rules for defining meso network nodes are automatically taken into account by Vissim when you create meso network nodes for a Vissim network, but not when you define them individually and manually in the Network editor.

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.

Length of meso edges

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.

If you define meso network nodes manually one by one and do not create all of them for the entire Vissim network, note the following points:

• Model small meso network nodes and make sure that the edges are long enough.
• Follow the rules and examples given for defining meso network nodes (Rules and examples for defining meso network nodes).

Requirements for modeling a Vissim network

Even if you create all meso network nodes for the entire Vissim network in a single step, Vissim can only insert these nodes if the following requirements for modeling outside of micro-simulation sections are met:

• In particular, the following must be defined: zone connectors, abstract parking spaces, inputs for public transport lines
• Vehicles must be able to leave sections for micro-simulation
• Network objects of the following types must not intersect or lie within conflict areas:
• Parking Lots
• Managed lanes routing decisions must not be defined within meso network nodes.
• Dynamic routing decisions must not be defined within meso network nodes either.
• Public transport stops
• Nodes
• Sections
• The lane and opposing lane do not overlap by more than 100 m.
• No lane conflict of a link within a meso network node may intersect the conflict area. Pay particular attention to this in the case of multiple lanes.