Node-edge graph

The graph used for simulation consists of nodes and edges. In general, the nodes in the graph correspond to the nodes in the network. However, zones are also represented by nodes in the graph. Edges are either within a node (turn edges) or between nodes (link edges). Link edges basically correspond to the connectors and links of the network. Link edges are generally characterized by the attributes of the respective link (e.g. number of lanes, v0). By default, the length of turn edges within a node is zero. In the example presented (Illustration 143), the edges of the graph correspond to Visum network objects, e.g. the length of the link edge corresponds to the length of the Visum link.

Illustration 143: Node-edge graph for Visum nodes with standard geometry

This standard case does not apply should node geometry and standard geometry differ, e.g. when there are pocket lanes, channelized turns or roundabouts. In these cases, additional nodes and edges are generated for the graph in Visum. In the following example Illustration 144 this is shown for pocket lanes at the inbound and/or outbound link. The additionally created nodes and edges of the graph cause the edges allocated to the Visum link and Visum turn to change. In this case, the link edges with two lanes between the nodes in the graph correspond to the Visumturn. The length of the Visum turn (attribute SBA length) is determined by the pocket length. The length of the links (attribute SBA length < length) is reduced accordingly.

Illustration 144: Node-edge graph for Visum nodes with pocket lanes

Table 148 contains attributes of node geometry used to create additional nodes in the node-edge graph for simulation.

Object	Parameters	Meaning	Control type affected
Leg	Is Channelized	Defines existence of a channelized turn	All except roundabout
Leg	Channelized control	Determines conflict and values of default parameters at end of the separate right turn	All except roundabout
Leg	Channelized turn length	Defines length of channelized turn	All except roundabout
Leg	Has bypass lane	Defines existence of bypass	Roundabout
Leg	Bypass control	Determines conflict and values of default parameters at end of the bypass	Roundabout
Leg	Bypass radius	Determines geometry of bypass	Roundabout
Leg	Roundabout inscribed circle diameter	Determines roundabout geometry	Roundabout
Leg	Number of conflicting lanes	Determines conflicts for the leg	Roundabout
Nodes	Roundabout circulating lane width	Determines roundabout geometry	Roundabout
Lane	Length	Defines length of pocket lane	All

Table 148: Additional input attributes for node modeling

From the input parameters, in particular, from the inputs of the node geometry, the length of link and turn edges of the graph are calculated and transferred to the allocated Visum network objects. This allocation has an impact on the allocation of output attributes. For example, travel times and delays can only occur at turns with a length greater than zero. If there is no pocket lane at a signal-controlled node, delays through the signal controller are only indicated at inbound links.

Object	Parameters	Meaning
Links / (main) turns / lanes	SBA length	Length of total of edges allocated to the Visum link, (main)turn and or lane.
Links	SBA capacity-PrTSys	Capacity calculated from the parameters of the car following model of TSys and max.link speed SBA Cap-PrTSys = (3600/temporal headway) x number of lanes with temp. headway = reaction timeTSys x factorLink + (eff. veh. lengthTSys) x factorLink/v0-PrTSys)

Table 149: Attributes calculated from the node-edge graph