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How to release vehicles onto the network via zones in Paramics

UPDATED: April 21, 2017


Zones are defined as specific points or areas in the study area that release vehicles onto the network. The exception to this definition is fixed route vehicles (PT vehicles) which can be generated from any PT stop in the network.

Paramics releases vehicles onto the network via zones. There are two different types of zones:

Internal Zones (Zones with Normal Nodes): 
Zones with Normal Nodes are designed to represent parts of the network in which vehicles are released onto the network from a stationary position. This can be used to represent residential areas, parking lots, parking rows etc.
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Vehicles will be released onto the network in accordance with the release probability at a starting speed of 0 mph/kph. In addition Zones with Normal Nodes will allow vehicles to be generated anywhere along the link (decided randomly) as long as there is enough space to do so safely. In this manner a vehicle is capable of being release in the path of a previously generated vehicle. This may happen to vehicles generated from the same zone of vehicles traveling through the zone.

Zones with Normal Nodes are not required to be dead end zones as External Zones. They can be used to represent a parking row or residential streets where disruption to traffic flow can be caused by vehicles entering the link from driveways or parking spaces.


External Zones (Zones with Connector Nodes): 

Zones with Connector Nodes are designed to represent points in the network at which vehicles load onto the network from a moving position in an existing traffic flow stream. This can be used to represent edges of the study area that are existing roads, the category of road or link is not important.
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Vehicles will be released onto the network in accordance with the release probability at a link speed. Vehicles generated from Zones with Connector Nodes will only be generated if there are no vehicles between the point it is going to be generated and the upstream end of the link. In this way vehicle are not forced to slow down 

Zones with Connector Nodes are required to be dead end zones as unlike Zones with Normal Nodes, which can be through links. They can be used to represent the edges of a study area where traffic flow enters in a natural way.

Note that the length of the release link/zone is a key factor in the links ability to store vehicles on the network rather than being blocked (stored off-network).

It is recommended that vehicles are introduced into the study area as they would appear in reality. From this perspective newly released vehicles do not behave in a natural manner if flows are moderate. Released vehicles are generated using the release probability and not in a "platooning" fashion or in accordance to traffic flow theory. It is advised that Zones with Connector Nodes (or links) be extended upstream beyond their physical point they represent in order to allow released vehicles the time/space to arrange themselves in accordance with car following and lane changing theory so that the enter the study are in a more natural state of flow depending on volume.
 

Environment Details

Products affected: Paramics®

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