Evaluating nodes

Using the node evaluation, you can record data from nodes of microscopic and mesoscopic simulation in the Vissim network (Modeling nodes). Node evaluation is used especially to determine specific data from intersections without first having to define all sections manually in order to determine the data.

Vehicle classes are grouped together

By default, the data for all vehicle classes is entered together. You can also show the data for certain vehicle classes separately in the evaluation (Configuring evaluations of the result attributes for lists).

Taking exhaust emissions into consideration

Node evaluation also determines exhaust emissions. The basis for these are formed by standard formulas for consumption values of vehicles from TRANSYT 7-F, a program for optimizing signal times, as well as data on emissions of the Oak Ridge National Laboratory of the U.S. Department of energy. The data refers to a typical North American vehicle fleet and does not differentiate between individual vehicle types. Thus node evaluation is used to compare the emissions of different scenarios. You can use the add-on modules EnViVer or Bosch if you want to determine emissions for individual vehicle types (Quick start guide Calculating emissions based on emission classes), (Calculate accurate emissions with Bosch Cloud Service).

Objects that are not considered

The node evaluation does not take into account:

• Vehicles on connectors for which the Reverse parking attribute is selected
• User defined orientations (Attributes of nodes)

Capturing queue lengths

If node evaluation is selected, queue lengths are determined for each turn relation in each node in which the attribute Use for evaluation is selected. These queue lengths each go from the position of a queue counter upstream out of the node, at most to the next evaluation node. These queue counters are created automatically by Vissim. The queue counter is positioned on the first of the following network elements in the course of the turn relation:

• Signal heads
• Stop line (red) of a priority rule
• Conflict area (red/green) where the turn relation requires waiting (red).

If none of these network elements is located on the turn relation, the queue counter is placed at the node entrance.

If upstream of the queue counter’s position several connectors lead to a link, the queue counter detects congestion along all of these connectors and outputs the length of the longest of these traffic jams.

Tip: You can visualize queue lengths in the network editor. (Graphic parameters for visualizing of queue lengths).

Capturing delays through travel time measurements

Delay measurements record the number of vehicles, average delays, average stop delays and the number of stops of a turn relation. Delay measurements consist of one or several travel time measurements. Vissim generates these delay and travel time measurements.

For each of the travel time measurements, the following applies:

• Travel time measurement begins upstream of the specified distance, before the node entry. For travel time measurements, the result attribute Start of delay segment before the node specifies this distance. The start section lies immediately downstream of the next upstream parking lot, if it has been assigned to a zone that allows cars for dynamic assignment.
• Travel time measurement starts immediately after the closest node, if there are no more than four junctions between the two nodes.
• Travel time measurement ends at the node exit.

PT stops at public transport stops are not counted as PT stops. Passenger service times of PT vehicles and the waiting time at stop signs are not accounted for in delay times. However, delays caused through braking just before a PT stop and accelerating again afterwards are included in delay times.

If an edge between nodes leads via more than three branchings, it is ignored during node evaluation. Here a branching is any connector that branches off a link upstream of the beginning of another connector or node entry.

If two or more nodes have an identical FromLink and ToLink, only one queue length is reported.

Ensuring minimum distance between the beginning of a link and a parking lot

In order for vehicles to be detected by the node evaluation at parking lots with zone connector, make sure that the distance from the beginning of the link or connector to the respective parking lot is not very short.

Output data and formats

You can save the following data and data formats:

Output	ASCII file	MDB table	Attribute file from attribute list
Aggregated data	-	-
Raw data	*.knr		-

• Show result attributes in attribute lists (Displaying result attributes in attribute lists)
• Show result attributes in a result list (Showing result attributes in result lists)
• Save raw data to a file or database (Configuring evaluations for direct output)

Notes: Make sure that: The attribute UseForEval (Use for evaluation) of nodes that you want to evaluate, is selected (Attributes of nodes). Nodes with the selected option UseForEval are active nodes, while they are passive nodes if the option is deactivated. Generate a node-edge graph (Generating a node-edge graph). Do not group larger network sections, containing multiple intersections, into a node.

Restrictions for nodes of mesoscopic simulation

• Only the number of vehicles and persons, the delay per vehicle and per person, and the level of service attributes are recorded and output.
• The values of queue lengths, stop delays, stops and emissions are empty or zero.
• The start section for each internal travel time measurement is placed at the beginning of the first meso edge. The latter must start at least as far upstream of the node as specified in the configuration of the node evaluation, in the Start of delay segment attribute.

Defining result evaluation for nodes

1.  From the Evaluation menu, choose > Configuration > Result Attributes tab.

2.  In the Nodes row, select Collect data.

3.  If desired, change the time and interval (Configuring evaluations of the result attributes for lists).

4.  Click the More button.

The window Node opens.

Element	Description
Delay segment start before the node (for node results and node raw data evaluation)	Distance [m] before node, from which delay time is measured
Queue definiton (for queues and node results): Define queue condition
Begin	A vehicle is in queue if its speed is less than the value v < that was entered for the Begin.
End	A vehicle remains in queue as long as its speed has not yet exceeded the value v > that was entered for the End.
max. clearance	Maximum net distance which can occur between two vehicles in queue. The queue is considered to be interrupted if there are larger gaps. Values between 10 and 20m are usual.
max. length	Maximum queue length. Longer queues may still occur. This attribute is useful if longer queues occur at the next node in the network, but the queues are to be evaluated separately for each intersection. When a large value, for example, 4 km, allows a long queue to form, the simulation speed decreases.
Consider adjacent lanes	Select this option to consider adjacent lanes when calculating the queue length for evaluation (Showing results of queue counters in lists).

Defining direct output of node evaluation

1.  From the Evaluation menu, choose > Configuration > Direct Output tab.

2.  In the Nodes (raw data) row, click the option of your choice: Write to file and/or Write database.

3.  If desired, change the time and interval (Configuring evaluations of the result attributes for lists).

4.  Click the More button.

The window Nodes (raw data) opens.

5.  Make the desired changes:

Element	Description
Start of delay segment before node	Distance [m] before node, from which delay time is measured

Result of node evaluation

The *.knr file contains the following data:

Attribute	Definition
VehNo	Vehicle number
VehType	Number of vehicle type
StartTime	Simulation second at which the vehicle enters the node
End at	Simulation second at which the vehicle exits the node
StartLink	Link number from which vehicle arrives at node
StartLane	Lane number from which vehicle arrives at node
StartPos	Position from the beginning of the link from which vehicle arrives at node
NodeNo	Node number
Movement	Cardinal points from-to, in which the vehicle moves through the node
FromLink	Number of link that leads to the node Note: This is the link with the shortest path to the node. This does not have to be the link via which the vehicle enters the node.
ToLink	Number of link that leads out of the node. The vehicle has left the node via this link.
ToLane	Number of lane that leads out of the node. The vehicle has left the node via this lane.
ToPos	Position of the node exit on the link which leads out from the node
Delay	Delay in seconds that it takes to leave the node starting from crossing the start section until leaving the node
StopDelay	Stop delay in seconds within the node starting from crossing the start section until leaving the node
Stops	Number of stops within the node starting from crossing the start section until leaving the node. This includes stopping at the turning point after backing out of the parking space before the vehicle continues driving forward.
No_Pers	Number of persons in the vehicle

Defining direct output of node evaluation

1.  From the Evaluation menu, choose > Configuration > Result Attributes tab.

2.  In the Nodes row, select Collect data.

3.  If desired, change the time and interval (Configuring evaluations of the result attributes for lists).

4.  Click the More button.

The window Node opens.

Example of node evaluation of raw data *.knr

Node evaluation (raw data)

            
File:    C:\Users\Public\Documents\PTV Vision\PTV Vissim 2024\Examples Demo\example.inpx
Comment:  Example, SC 3-10

Date:    03.01.2024 12:23:33

PTV Vissim 2024.00-00* [253691]

VehNo; VehType; TStart; TEnd; StartLink; StartLane; StartPos; NodeNo; Movement; FromLink; ToLink; ToLane; ToPos; Delay; StopDelay; Stops; No_Pers;
   2;   100;       1.7;      7.0;        4;                 1;    0.000;        1;   S-N;      4;      4;               1; 77.268;         0.0;       0.0;     0;       1;

   3;   100;       3.0;      8.2;        4;                 1;    0.000;        1;   S-N;      4;      4;               1; 77.268;         0.0;       0.0;     0;       1;

   1;   100;       1.1;      9.5;        1;                 1;   11.013;        1; SW-NE;      1;      1;               1; 144.237;        0.0;       0.0;     0;       1;

...

Results list Node results

The results list Node results may contain the following data in addition to the above described result attributes of the *.knr file:

Attribute	Definition
EmissionsCO	Emissions CO: Quantity of carbon monoxide [grams]
EmissionsNOx	Emissions NOx: Quantity of nitrogen oxides [grams]
EmissionsVOC	Emissions VOC: Quantity of volatile organic compounds [grams]
Movement	Movement: Number of connectors of a specific inbound link to a specific outbound link of a node. A movement may contain multiple link sequences, for example via parallel connectors. In Node evaluation, various result attributes are automatically calculated for the individual movements. Number and name of node Number and name of the FromLink, which leads to the node Position of FromLink, at which it passes into the node. Number and name of the ToLink, which leads from the node Position of ToLink, at which it leaves the node. Movements are created for all possible pair options of inbound and outbound links. The Total movement contains all movements of each node. The last row of a node movement always contains the Total movement. It is only listed specifying the node name and number. To show result attributes of movements, you first need to generate the node-edge graph for evaluations (Generating a node-edge graph).
Vehs	Number of vehicles
FuelConsumption	Fuel consumption [US liquid gallon]
VehDelay	Vehicle delay (Showing delay measurements in lists)
PersDelay	Person delay (Showing delay measurements in lists)
LOS(All)	Level of service (transport quality): The levels of transport quality A to F for movements and edges, a density value (vehicle units/mile/lane). It is based on the result attribute Vehicle delay (average). The current value range of vehicle delay depends on the Level of service scheme type of the node Signalized or Non-signalized (Attributes of nodes). The LOS in Vissim is comparable to the LOS defined in the American Highway Capacity Manual of 2010.   Signalized intersection Non-signalized intersection LOS_A Delay < 10 s or no volume, as no vehicle is moving, also due to traffic jam LOS_B > 10 s to 20 s > 10 s to 15 s LOS_C > 20 s to 35 s > 15 s to 25 s LOS_D > 35 s to 55 s > 25 s to 35 s LOS_E > 55 s to 80 s > 35 s to 50 s LOS_F > 80 s > 50 s
LOSVal(All)	Level-of-service value: Level of transport quality as numbers from 1 to 6 according to the LOS scheme assigned. No value = no volume. 1 corresponds to LOS_A < 10 s, up to 6 corresponds to LOS_F. The level-of-service value is more suitable for user-defined formula attributes and color schemes.
Simulation run	Number of simulation run
Queue length	Mean of all average queue lengths in a node. Vissim automatically generates queue counters in a node to detect queue lengths. Vissim calculates the average queue length detected by queue counters in a node and then calculates their mean.
Queue length (maximum)	Maximum queue length. The result depends on the attribute Consider adjacent lanes.

The attributes will be shown line-by-line for each simulation run and every movement in the node.

For each node, the total results in a later row will show:

• Calculation of the total for vehicles, persons, emissions, fuel consumption
• Calculation of total average for vehicle delay, person delay, stopped delay, queue length, stops
• Calculation of the maximum queue length (maximum)